ELECTRONIC TROUBLESHOOTING 3176 DIESEL TRUCK ENGINE Caterpillar

These tests are designed to establish whether a component and related parts are working correctly and if not, to pinpoint the faulty component.

These tests may also be used for basic health checks, to determine if problems exist, or as a guide to check for intermittent problems.

P-201: Inspecting Electrical Connectors

Many of the Operational Procedures and Diagnostic Code Procedures in this troubleshooting guide will direct you to check a specific electrical connector. Use the following steps to help determine if the connector is the cause of the problem. If a problem is found in the electrical connector, repair the connector and continue the test procedure.

1. Check connector lock ring.

Make sure the connector was locked correctly and the lock ring is capable of locking the connector together.

2. Perform 10 pound pull test on each pin/wire.

Each pin and connector should easily withstand 10 pounds of pull and remain in the connector body. This test checks whether the wire was correctly crimped in the pin and whether the pin was correctly inserted into the connector. Repair as needed.

Any time a wire is removed from a connector for testing purposes, repeat the 10 pound pull test on the wire after re-inserting it into the connector, to be sure it was properly installed.

NOTE: Pins should ALWAYS be crimped onto the wires; NEVER soldered. Use 1U5804 Crimping Tool (part of 4C3406 Connector Repair Kit).

3. Visually inspect wiring.

Look for worn or abraded wires. Check for pinched or damaged harnesses.

4. Visually inspect connectors.

Verify that pins and sockets are not corroded or damaged. Verify correct alignment and location of pins in the connector.

5. Check individual pin, socket and connections.

This is especially important for intermittent problems. Using a new pin, insert the pin into each socket one at a time to check for a good grip on the pin by the socket. Repeat for each pin on the mating side of the connector, using a new socket for the test.

P-210: Electrical Power Supply Test

The Electronic Control Module (ECM) of the 3176 System, receives electrical power (battery voltage) through wiring supplied by the vehicle manufacturer. In typical applications, the 3176 System receives power whenever the key is turned on.

Some vehicles may be equipped with an engine protection shutdown system (such as a Kysor or Vigil shutdown system). An idle time shutdown system (external to the 3176 System) may also be used. These devices interrupt electrical power to the ECM, to shut the engine down. Some of these devices will not supply power to the ECM until the engine is cranked, until oil pressure comes up to acceptable limits, or until an override button is pressed. Keep in mind that these devices may be the cause of loss of (or intermittent) power to the ECM.

This procedure tests whether correct voltage is being supplied by the vehicle wiring. Detailed tests to identify specific failures in the vehicle wiring are the responsibility of the vehicle manufacturer.

Note that the ECAP or DDT is supplied with electrical power through connections in the 3176 Engine Wiring Harness. Therefore, if the ECAP or DDT has power, the ECM probably does also.

For intermittent problems that could be caused by vehicle wiring (such as intermittent shutdowns), temporarily bypassing the vehicle wiring may be an effective means of determining if the problem is in the engine or the vehicle wiring. If symptoms are not present when the vehicle wiring is bypassed, then the engine and engine wiring are probably not defective, and vehicle wiring is probably causing the fault. A means of bypassing vehicle wiring is explained later in this procedure.

Step 1. Check Electrical Connectors And Wiring

Check Power/Data Link Connector (J8/P8), battery connection and grounds to J8/P8, being sure to:

* Visually and physically check ground connections for looseness or corrosion, particularly the connections at the battery posts, the starter posts and the cylinder head grounding stud. If a problem is found, disconnect, clean, and reconnect the connector

* Perform 10 pound pull test on each pin or wire.

* Inspect wiring for pinch points or abrasion.

* Inspect connectors for damage or corrosion. Refer to P-201: Inspecting Electrical Connectors for details.

Step 2. Check Battery Voltage Coming To ECM

A. Connect 9-Pin Breakout 'T' at Power/Data Link Connector (J8/P8).

B. Turn key ON (engine off).

C. Measure the voltage between + Battery (Pin A) and - Battery (Pin B).

The battery voltage should be between 11.5 and 13.5 volts DC.

OK: The ECM is currently receiving the correct voltage. If intermittent problems with battery voltage may be occurring, consider temporarily bypassing vehicle wiring as shown in Step 3. Otherwise, Stop.

NOT OK: The ECM is NOT receiving the correct voltage. If voltage is less than 2 volts DC, check for loose connections in vehicle wiring leading to Power/Data Link Connector (J8/P8) (see Step 1). If voltage is between 2 and 11.5 volts DC, load test batteries. Refer to Operating Manual, Form No. SEHS9249, Use Of The 4C4911 Battery Load Tester and Special Instruction, Form No. SEHS7633, Battery Test Procedure.

Step 3. Bypass Vehicle Wiring For Testing

NOTE: This bypass is for TEST PURPOSES ONLY. It may be left on the vehicle temporarily to test whether intermittent problems are due to interruptions in battery power to the ECM. Since this will also bypass any engine protection devices, obtain approval from the owner before releasing a truck with this bypass installed. The bypass switch is installed in parallel with the ignition switch. Either one will turn power ON, and both must be OFF to turn power OFF and shutdown the engine.

A. Build a bypass circuit as shown in the illustration, using #14 AWG wire.

B. Connect the battery end of the bypass DIRECTLY to the (+) Battery post.

C. Remove Pin A (+ Battery) from P8 (Power/Data Link Connector - vehicle side).

D. Insert the other end of the bypass into P8, Pin A (as shown).

E. After the engine has started, then connect the wire that was originally in P8, Pin A to the wire spliced into the bypass, as shown above. This supplies voltage to the Throttle Position Sensor, Vehicle Speed Buffer and Diagnostic Lamp.

Tape all temporary connections tightly to keep them clean, to prevent shorting to ground and to prevent loosening during vehicle operation.

F. Turn the ignition key OFF. This will isolate the 3176 System from the original vehicle power circuit.

G. Install the temporary switch in the cab. It will take the place of the normal ignition switch during testing.

H. After tests are complete, restore all wiring to original condition.

The engine should perform normally with the bypass installed.

OK: If symptoms disappear when the bypass is installed, but come back when it is removed, the problem is in the vehicle wiring that supplies power to the ECM.

NOT OK: If symptoms continue when the bypass is installed, the problem is in the 3176 System. Continue with the procedure in this manual best describing the symptom(s).

P-211: Throttle Position Sensor Test

The Throttle Position Sensor (TPS) is used to provide a throttle position signal to the ECM. The Throttle Position Sensor may be one of two types. The "Remote-Mounted" TPS is about the size of a soft drink can and is connected to the throttle pedal by OEM-supplied linkage. It requires adjustment for correct operation (see procedure P-303). The "Pedal-Mounted" TPS is mounted directly to a specific style of throttle pedal and requires no adjustment and in fact, can not be adjusted. Both sensors provide the same type of signal to the ECM.

Sensor output is a constant frequency signal whose pulse width varies with throttle position. This output signal is referred to as either "Duty Cycle" or a "Pulse Width Modulated (PWM)" signal and is expressed as a percentage. The "Pedal-Mounted" TPS will produce a "Duty Cycle" of 10 to 22% with the pedal released and 75 to 90% with the pedal fully depressed. The "Remote-Mounted" TPS should produce a duty cycle of 15% to 20% with the pedal released and 80% to 85% with the pedal fully depressed when the sensor is correctly adjusted. This is then translated by the ECM into a "Throttle Position" of 3% with the pedal released to 100% with the pedal fully depressed.

Step 1. Check Electrical Connectors And Wiring

Check the Vehicle Connector (J7/P7), Throttle Position Sensor (J11/P11) and ECM (J4/P4) connectors and the wiring between them being sure to:

* Check Connector lock rings

* Perform 10 pound pull test on each pin or wire

* Inspect wiring for damage or abrasion

* Inspect connectors for damage or corrosion. Refer to P-201: Inspecting Electrical Connectors for details. Repair any damage, then continue with the next step.

Step 2. Check Throttle Position Sensor Adjustment

A. If equipped with a "Pedal-Mounted" Throttle Position Sensor, check pedal and sensor for damage, then proceed to Step 3.

B. Refer to procedure P-303: Throttle Position Sensor Adjustment to determine if the sensor is correctly adjusted.

The sensor should be able to be correctly adjusted as explained in P-303.

OK: Adjustment is correct. Continue to next step.

NOT OK: The sensor could not be adjusted correctly. There is a problem with the sensor circuit. Proceed to Step 4.

Step 3. Check Throttle Position Reading

A. Turn key OFF, then back ON.

B. Observe the "Throttle Pos" reading on the "Display Status" screen of the ECAP or DDT while pressing and releasing the throttle.

The "Throttle Pos" should read 3% with the throttle pedal released and progressively increase to 100% when the throttle pedal is fully pressed.

OK: The Throttle Position Sensor is currently operating correctly. Stop.

NOT OK: There is a problem with the Throttle Position Sensor circuit. Continue to next step.

Step 4. Check Throttle Position Sensor Voltage Supply

A. Install a 3-Pin Breakout 'T' at the Throttle Position Sensor Connector (J11/P11).

B. Measure the voltage between + Battery (Pin A) and Throttle Return (Pin B) on the Breakout 'T'.

The supply voltage to the sensor should be between 11.5 and 13.5 volts DC.

OK: Voltage supply OK. Continue to next step.

NOT OK: The Throttle Position Sensor is not being supplied with the correct voltage. Inspect the vehicle wiring for cause of problem. Stop.

Step 5. Check Throttle Position Sensor Output Duty Cycle At Throttle Sensor

A. Remove Throttle Sensor Wire (Pin C) from J11. (This disconnects vehicle wiring from the sensor).

B. Connect the ECAP or DDT's PWM probe to Pin C of the Breakout 'T'.

C. Use the ECAP or DDT to display the Duty Cycle output of the Throttle Position Sensor while pressing and releasing the pedal.

D. Reinsert wire C in J11.

The DUTY CYCLE should be between 10 and 22% with throttle pedal released and increase to between 75 and 90% with the throttle pedal fully depressed.

OK: The Throttle Position Sensor is OK. Continue to next step.

NOT OK: The Throttle Position Sensor is defective or out of adjustment. Check pedal and linkage for damage. Check the adjustment for the sensor (Remote Mounted Sensor only) if it has not been previously checked, if no damage is found, replace the sensor. Stop.

Step 6. Check Throttle Position Sensor Duty Cycle At Vehicle Connector

A. Install the 9-Pin Breakout 'T' at J7/P7.

B. Connect the PWM probe to Pin E on the Breakout 'T'.

C. Use the ECAP or DDT to display the Duty Cycle of the Throttle Position Sensor while pressing and releasing the pedal.

The DUTY CYCLE should be between 10 and 22% with throttle pedal released and increase to between 75 and 90% with throttle pedal fully depressed.

OK: A good Throttle Position Signal is reaching the Vehicle Connector. Continue to next step.

NOT OK: The harness is damaged between J7/P7 and J11/P11. Inspect and repair as necessary. Stop.

Step 7. Check Throttle Position Sensor Duty Cycle At ECM

A. Install the 40-Pin Breakout 'T' at ECM Connector (J4/P4).

B. Connect the PWM probe to Pin 8, on the Breakout 'T'.

C. Display Duty Cycle on the ECAP/DDT while pressing and releasing the throttle pedal.

The Duty Cycle should be between 10% and 22% with the throttle pedal released and increase to between 75 and 90% with the throttle pedal fully depressed.

OK: A good Throttle Position Signal is reaching the ECM. If there was a problem with the throttle position sensor circuit in Step 3, then the problem is in the ECM. Replace the ECM. Stop.

NOT OK: The wiring harness is damaged between the Vehicle Connector and the ECM. Repair as needed. Stop.

P-212: Diagnostic Lamp Test

The Diagnostic Lamp is used to indicate the existence of a fault, to indicate "Driver Alert" status of the Idle Shutdown Timer and may be used to read Diagnostic Codes. While the engine is operating, it will go on for a minimum of 5 seconds any time a fault condition exists. It will remain on as long as the fault is ACTIVE.

When the ECM is first powered up, the lamp comes ON for 5 seconds, blinks OFF, comes ON for another 5 seconds, then goes OFF. After this time, any ACTIVE diagnostic codes will be flashed out, as well as any Diagnostic Codes which have occurred since power-up.

ACTIVE Diagnostic Codes, as well as any Diagnostic Codes occurring since power-up, may be viewed at any time by turning the cruise ON/OFF switch to OFF and holding the SET/RESUME switch in the RESUME position until the lamp begins to flash, then releasing it.

One terminal of the Diagnostic Lamp is connected to battery voltage through the 10 Amp. Sensor Fuse, whenever the key is ON. The other terminal is connected to the ECM through Pin G of the Power/Data Link Connector and Pin 4 of the ECM Connector (P4/J4). The ECM brings this signal to less than 2 volts DC, to turn the Diagnostic Lamp ON.

Pin 4 of the ECM Connector (J4/P4) will be at battery voltage when the lamp is OFF and less than 2 volts DC when the lamp is turned ON.

Step 1. Test Lamp Through ECM

Turn key ON (engine OFF).

The lamp should turn ON for 5 seconds, blink OFF, turn on for another 5 seconds, turn OFF, then flash ACTIVE Diagnostic Codes, if any are present.

OK:Lamp is working normally. Stop.

NOT OK:Lamp is not working correctly. Continue to next step.

STEP 2. Bypass The ECM

Remove wire from Pin 4 of the ECM Connector (P4) (harness side) and ground the wire.

With key ON (engine OFF), the lamp should come ON and stay ON.

OK:The lamp circuit is OK, but the ECM is not grounding lamp. Verify that the ECM is receiving battery voltage, if so replace the ECM. Stop.

NOT OK:Verify that the bulb has not burned out. If bulb is good, the problem is in the vehicle wiring. Stop.

P-213: Vehicle Speed Signal Test

The vehicle speed circuit consists of the Vehicle Speed Sensor, the Vehicle Speed Buffer and associated wiring. The sensor is a standard magnetic pickup and is supplied by the truck manufacturer. It senses the movement of teeth on the output shaft of the transmission. The buffer (Caterpillar supplied) takes the signal from the sensor, conditions it and sends it to both the ECM and the vehicle speedometer.

One of two types of Vehicle Speed Buffers may be used. The 3E0020 Buffer is an improved version of the 7T6398 and is a direct pin-for-pin replacement. Either buffer should be grounded at the same point as the ECM (cyclinder head ground stud) to minimize "electrical noise" in the ground circuit. Note that digital return may also be used for the vehicle speed buffer ground if the installation has been reviewed by Caterpillar.

There are three acceptable options for wiring of the vehicle speed circuit:

NOTE: For all three options, the Vehicle Speed Buffer should be grounded to the same ground point as the ECM. This is true for either the 7T6398 or the 3E0020 Vehicle Speed Buffer. On 3176 Engines, the ECM ground point is the cyclinder head ground stud.

Option 1. Use separate sensors for the Vehicle Speed Buffer and the speedometer, with the second sensor supply the signal to the speedometer. This option completely isolates the two circuits and is preferred by Caterpillar. See Illustration 1.

Illustration 1
Recommended vehicle speed circuit wiring when using two separate sensors. For 3E0020 or 7T6398 Vehicle Speed Buffer.

Option 2. Use a single sensor, with the Vehicle Speed Buffer supplying the signal to the speedometer. This option provides good results when correctly wired. When using the 7T6398 Vehicle Speed Buffer, the circuit should be wired as shown in illustration 2a. The ground connection for the speedometer should be connected to the cylinder head ground stud. It SHOULD NOT be connected to the cab ground. Note that this illustration is electrically identical to the schematic in the 3176 Diesel Truck Engine Electrical Schematic, Form No SENR3912, which is in the complete Service Manual, 3176 Diesel Truck Engine, Form No. SENR3910, but shows the required grounding for the speedometer more clearly.

Illustration 2a
Recommended vehicle speed circuit wiring when using a single sensor with 7T6398 Vehicle Speed Buffer. (See Illustration 2b for 3E0020 Vehicle Speed Buffer).

When using a single sensor with the 3E0020 Vehicle Speed Buffer, the circuit should be wired as shown in Illustration 2b. Improvements included in the new 3E0020 Vehicle Speed Buffer allow the speedometer to be grounded as shown. The new buffer also provides a second output line for speedometers requiring two signal lines.

Illustration
2b Single sensor wired as recommended for 3E0020 Vehicle Speed Buffer. (See Illustraton 2a for 7T6398 Vehicle Speed Buffer).

Option 3. Use a dual winding sensor, with the second winding supplying the signal to the speedometer. This option is not preferred by Caterpillar, but can provide acceptable results if the sensor is installed correctly. Dual winding sensors may be used in some new OEM installations which have been specifically reviewed by Caterpillar.

Illustration 3
Recommended vehicle speed circuit wiring when using a dual-winding sensor. For 3E0020 or 7T6398 Vehicle Speed Buffer.

The Vehicle Speed Buffer has a five-pin connector (J14/P14) with pins to battery negative, battery positive, the ECM and two for the vehicle speedometer.

+ Battery (Pin A) supplies battery power to the buffer. - Battery (Pin B) provides battery ground through the cylinder head ground stud.

Buffer Output to the ECM (Pin D) supplies a series of 5 volt DC pulses to the ECM. The frequency of the pulses varies directly with the speed of the vehicle.

When a single Vehicle Speed Sensor is used, as in Illustration 2a and 2b, the vehicle speed signal to the speedometer is provided by the buffer. The signal from the 3E0020 Buffer (later) is different than the signal from the 7T6398 Buffer (earlier):

* The 3E0020 buffer has two speedometer outputs, one at P14, Pin C and one at P14, Pin E. Output at each one is a series of -8 volt to +8 volt pulses. The two outputs oppose one another; when Pin C is at +8 volts, Pin E is at -8 volts, and vice versa. Either or both outputs may by used.

* The 7T6398 buffer has one speedometer output of -2.5 to +2.5 volt pulses at P14, Pin C. P14, Pin E is not used on the 7T6398.

Test Procedure:

Step 1. Check Electrical Connectors And Wiring

Check ECM connector (J4/P4) and Vehicle Speed Buffer connector (J14/P14) and wiring between them, being sure to:

* Check Connector lock rings.

* Perform 10 pound pull test on each pin or wire.

* Inspect wiring for damage or abrasion.

* Inspect connectors for damage or corrosion. Refer to P-201: Inspecting Electrical Connectors for details. Repair any damage, then continue with the next step.

Step 2. Inspect Sensor

Remove the Vehicle Speed Sensor(s) from the transmission and inspect for steel shavings and debris, or damage. Wipe sensor(s) clean. Test sensor according to manufacturer's instructions (sensor is OEM supplied).

OK: Continue to next step.

NOT OK: If sensor is damaged or does not operate correctly, replace sensor. Stop.

NOTE: Shavings and debris on the sensor may recur unless the transmission fluid is drained and replaced.

Step 3. Use ECAP/DDT To Check Speedometer With Truck Parked, Engine Running

Install ECAP or DDT and operate the engine with truck parked, not moving. Try several engine speeds.

The vehicle speedometer and ECAP/DDT should remain at zero mph.

OK: Continue to next step.

NOT OK: Speedometer is giving false readings, probably due to poor grounding. Check that buffer and speedometer grounds are as recommended (see illustrations). Stop.

Step 4. Check Vehicle Speed Correlation

Dyno test or road test vehicle. Compare mph on ECAP/DDT display against speedometer and against actual vehicle speed as measured on a dyno or by stopwatch.

ECAP/DDT and speedometer should agree with actual speed.

OK: Vehicle speed circuit is working normally. Stop.

NOT OK:

* If speedometer is inoperative, intermittent, or inaccurate, repair speedometer circuit or recalibrate speedometer. Stop.

* If ECAP/DDT reading is stable but inaccurate, refer to P-304: Vehicle Speed Calibration and calculate new scale factor. Enter the new scale factor into the 3176 System using the ECAP/DDT. Repeat Step 4. Stop.

* If ECAP/DDT reading is absent or intermittent, continue to next step.

Step 5. Check Buffer Supply Voltage

A. Install a 5-Pin Breakout 'T' on the vehicle speed buffer connector at J14 (vehicle wiring side only).

B. Turn key ON (engine off) and measure voltage from + Battery (Pin A) to - Battery (Pin B).

Buffer supply voltage should read 11.5 to 13.5 volts DC.

OK: Voltage to the buffer is correct. Continue to next step.

NOT OK: The buffer is not getting correct voltage. Check and repair OEM supplied wiring. Stop.

Step 6. Check Buffer Signal With Truck Parked, Engine OFF (7T6398 only)

NOTE: For 3E0020 go to Step 7.

A. Check Buffer Operation

Disconnect the wires (at Vehicle Speed Sensor) between the Vehicle Speed Sensor and the Vehicle Speed Buffer. Install a 5-Pin Breakout 'T' at the Vehicle Speed Buffer connector (J14/P14). Remove Wire D from J14 (vehicle side). Turn key ON (engine off) and measure Vehicle Speed Signal voltage between Pin D and Pin B. Alternately connect together and disconnect from each other, the Vehicle Speed Sensor wires.

Vehicle Speed Signal Voltage between Pin D and Pin B should be 4.5 to 8 volts DC with the Vehicle Speed Sensor wires disconnected and less than 1 volt DC with the wires connected.

OK: Vehicle Speed Buffer operation is correct. Continue to next step.

NOT OK: Vehicle Speed Buffer is not supplying the correct signal voltage to the ECM. Replace the Vehicle Speed Buffer. Stop.

B. Check Vehicle Speed Signal Coming To ECM

Reinsert the wire into Pin D of J14, leaving the Vehicle Speed Sensor disconnected from the Vehicle Speed Buffer. Install a 40-Pin Breakout 'T' at the ECM Connector (J4/P4). Measure the vehicle speed signal voltage between Pin 18 and Pin 12, on the Breakout 'T'.

Vehicle Speed Signal Voltage should be 4.5 to 8 volts DC.

OK: The Vehicle Speed Signal is reaching the ECM. If Step 4 indicated that no Vehicle Speed Signal was being displayed, then the ECM is defective. Replace the ECM. Stop.

NOT OK: The Vehicle Speed Signal is not reaching the ECM. Repair fault in harness between the Vehicle Speed Buffer and the ECM. Stop.

Step 7. Check Buffer Signal With Truck Parked, Engine OFF (3E0020 only).

NOTE: For 7T6398 go to Step 6.

A. Check Buffer Operation

1. With key OFF, install 5-Pin Breakout 'T' to Vehicle Speed Buffer Connector (J14/P14). Remove wires from Pins C, D, and E of J14 (vehicle side) and note location for re-installation.

2. Disconnect the Vehicle Speed Buffer input wires at the Vehicle Speed Sensor. Connect the white input wire to + Battery (Pin A, P14) on the 5-Pin Breakout 'T'.

3. Turn key ON (engine off). Measure voltage between -Battery (Pin B) and Pins C, D, and E on the 5-Pin Breakout 'T' (white input wire jumpered to Pin A, P14).

The voltages should read as shown below:

Pin D: Less than 1.0 volts DC

Pin C: -4.0 to -12.0 volts DC

Pin E: +4.0 to +12.0 volts DC

4. Move the white input wire (jumper) to - Battery (Pin B, P14) and take the readings again. Voltages should now be the opposite:

Pin D: +4.5 to +8 volts DC

Pin C: +4.0 to +12.0 volts DC

Pin E: -4.0 to -12.0 volts DC

5. After taking readings, reinsert wires into Pins C, D, and E of J14.

OK: Buffer is working correctly. Continue to next step.

NOT OK: Buffer is not working correctly. Replace buffer. Stop.

B. Check Harness Between Buffer And ECM

1. The white wire from the Vehicle Speed Sensor should still be connected to Pin B, P14.

2. Install a 40-Pin Breakout 'T' at the ECM Connector (J4/P4). Measure the Vehicle Speed Signal voltage between Pin 18 and Pin 12 on the Breakout 'T'.

The voltage should be 4.5 to 8 volts DC.

OK: The vehicle speed signal is reaching the ECM. If Step 4 found that no Vehicle Speed Signal was being displayed, then the ECM is defective. Replace the ECM. Stop.

NOT OK: The vehicle speed signal is not reaching the ECM. Repair fault in harness between the Vehicle Speed Buffer and the ECM. Stop.

P-214: Cruise Control And PTO Switches Test

The 3176 Cruise Control operates similar to automotive cruise controls. PTO mode operates similar to cruise, only it governs engine speed with the vehicle stationary. Five switch inputs to the 3176 System affect cruise or PTO:

1. CRUISE ON/OFF

This switch must be ON for cruise or PTO to be activated. The signal goes to the Vehicle Connector (J7/P7), Pin F.

2. SET/ACCEL

With the ON/OFF switch ON, momentarily pressing this switch will activate cruise (or PTO) and will tell the cruise or PTO to try to maintain the current speed. Holding this switch ON will cause cruise or PTO to slowly accelerate this setpoint. The signal goes to the Vehicle Connector (J7/P7), Pin J.

3. RESUME/DECEL

With the ON/OFF switch ON, momentarily pressing this switch will also activate cruise (or PTO) and tell the cruise or PTO to resume with the setpoint used when cruise was last disabled. Holding this switch ON will cause cruise or PTO to slowly decelerate this setpoint. The signal goes to the Vehicle Connector (J7/P7), Pin H.

4. CLUTCH

Depressing the clutch pedal will cause cruise or PTO to deactivate. The clutch signal goes to the Vehicle Connector (J7/P7), Pin G.

5. BRAKE

Depressing the brake pedal will cause cruise or PTO to deactivate. The brake signal goes to the Vehicle Connector (J7/P7), Pin C.

NOTE: All these switches are typically in the truck cab and are supplied by the OEM. To troubleshoot the ON/OFF, SET, or RESUME switches, use this procedure. To troubleshoot the CLUTCH or BRAKE switches, use P-215: Service Brake And Clutch Switch Test.

Voltage at each of the switch inputs to the ECM should be 5.0 ± 0.5 volts DC with the switch open (or OFF) and less than 0.5 volts with the switch closed (or ON).

Step 1. Check Switch Status On ECAP Or DDT

A. Install ECAP or DDT and turn key ON (engine off).

B. Operate CRUISE ON/OFF switch while observing status of 'Cruise/PTO Sw'.

C. Operate SET/ACCEL switch while observing status of 'Set Sw'.

D. Operate RESUME/DECEL switch while observing status of 'Resume Sw'.

The status of each should read 'ON' with the switch ON, and 'OFF' with the switch OFF.

OK: The switches are operating normally. Stop.

NOT OK: The ECM is not seeing the switch status change. Continue with next step.

Step 2. Check Switch Resistance At Vehicle Connector

A. Install the 9-Pin Breakout 'T' on the Vehicle Connector (J7/P7).

B. Set multimeter on 20,000 ohms (20K) scale and measure the resistance from each switch output terminal (shown in Table A) to the cylinder head ground stud. Operate each switch and measure the resistance with switch 'ON' and with switch 'OFF'.

The resistance should be as shown in Table A.

OK: Vehicle wiring checks OK. Continue to next step.

NOT OK: There is a problem in the switches or the vehicle wiring. Repair as needed using the OEM wiring schematics or refer to the OEM Dealer. Stop.

3. Check Switch Resistance At ECM

A. Reconnect Vehicle Connector (P7 to J7).

B. Install the 40-Pin Breakout 'T' at the ECM Connector (P4) on Wiring Harness side (P4) ONLY.

C. Set multimeter on 20,000 ohms (20K) scale and measure the resistance from each switch output terminal (shown in Table B) to both: - Battery (P4, Pin 12) and to the cylinder head ground stud. Operate each switch and measure the resistance with switch 'ON' and with switch 'OFF'.

The resistance should be as shown in Table B.

OK: The 3176 Wiring Harness checks good. If Step 1 found that the ECM is not seeing the switch status change, then the ECM is getting the correct signals, but is not reading them correctly. Check that the ECM is receiving correct battery voltage. If so, replace the ECM. Stop.

NOT OK: There is a problem in the 3176 Wiring Harness or the connectors between the vehicle connector and the ECM. Repair as needed. Stop.

P-215: Service Brake And Clutch Switch Test

The Brake and Clutch Switches are used in Cruise Control or PTO Mode to discontinue cruise or PTO operation. The switches may also be used to override the Idle Shutdown Timer.

The Brake and Clutch Switches are normally closed with one side of each switch connected to - Battery. Depressing either the clutch or brake pedal will discontinue PTO or Cruise Control operation. The clutch signal goes to the ECM through P7/J7, Pin G and the brake signal through P7/J7, Pin C. Voltage at Pin G and Pin C should be 5.0 ± 0.5 volts DC when that switch is open and less than 0.5 volts when that switch is closed.

Vehicle wiring for an engine brake may affect operation of this circuit. For example, the switch to turn the engine brake on may open this circuit (similar to turning the service brake on). Refer to the OEM Service Manual for the vehicle, to determine how the engine brake is wired.

Both the brake and clutch switches are OEM supplied. The brake switch is typically a pressure switch. The clutch switch is typically a limit switch mounted near the clutch pedal. The clutch switch is usually adjustable and should be adjusted so that some resistance is felt on the pedal before the switch opens.

Step 1. Check Brake Switch Status With ECAP/DDT

A. Install ECAP or DDT and turn key ON (engine off).

B. Operate the service BRAKE pedal while observing status of the 'Brake Sw' display.

C. Operate the CLUTCH pedal while observing status of the "Clutch Sw" display.

The status of the Service Brake Switch should be "OFF" when the BRAKE pedal is released and "ON" when the pedal is depressed.

The status of the Clutch Pedal Switch should be "OFF" when the clutch pedal is released and "ON" when the pedal is depressed. There should be resistance on the clutch pedal before the clutch switch engages.

OK: The Clutch and Brake Switches are operating normally. Stop.

NOT OK: Check adjustment of the clutch switch, then repeat this step. If the ECM is still not seeing the switch status change, continue to next step.

Step 2. Check Switch Resistance At Vehicle Connector

A. Install 9-Pin Breakout 'T' on Vehicle Connector (J7/P7).

B. Set multimeter on 20,000 ohms (20K) scale and measure the resistance from each switch output terminal (shown in Table A) to the cylinder head ground stud. Operate the clutch and brake pedals and measure the resistance with each pedal released and depressed.

The resistance should be as shown in Table A.

OK: Vehicle wiring checks good. Continue to next step.

NOT OK: There is a problem in the vehicle wiring. Repair as needed using the OEM wiring schematics or refer to the OEM Dealer. Stop.

Step 3. Check Switch Resistance At ECM

A. Reconnect the Vehicle Connector (P7 to J7).

B. Install the 40-Pin Breakout 'T' on the harness side of the ECM Connector (P4) ONLY (not J4).

C. Set multimeter on 20,000 ohms (20K) scale and measure the resistance from each switch output terminal (shown in Table B) to both: - Battery (P4, Pin 12) and to the cylinder head ground stud. Operate the clutch and brake pedal and measure the resistance with pedal "RELEASED" and with pedal "DEPRESSED".

The resistance should be as shown in Table B.

OK: The 3176 Wiring Harness checks good. If Step 1 found that the ECM is not seeing the switch status change, then the ECM is getting the correct signals, but is not reading them correctly. Check that the ECM is receiving correct battery voltage. If so, replace the ECM. Stop.

NOT OK: There is a problem in the 3176 Wiring Harness or the connectors between the Vehicle Connector and the ECM. Repair as needed. Stop.

P-216: Parking Brake Switch Test

The Parking Brake Switch is used only to enable the Idle Shutdown Timer. The Idle Shutdown Timer will only be activated when the parking brake is ON.

The Parking Brake Switch is supplied by the OEM. It should be normally closed (with brake applied and no air pressure to the parking brake) and connected to ground. Releasing the brake should open the circuit. The Idle Shutdown Timer will NOT operate unless the switch is installed to connect the parking brake input to ground.

The signal goes to the ECM through the Vehicle Connector (P7/J7), Pin B. Voltage at Pin B should be 5.0 ± 0.5 volts with the switch open (parking brake released) and less than 0.5 volts with the switch closed (parking brake applied).

Step 1. Check Switch Status With ECAP/DDT

A. Install ECAP or DDT and turn key ON (engine off).

B. Operate the PARKING BRAKE while observing status of the "Park Brake Sw" screen.

Switch status should be "OFF" with the brake released and "ON" with the brake applied.

OK: The Parking Brake Switch is operating normally. Stop.

NOT OK: The ECM is not seeing the switch status change. Continue to next step.

Step 2. Check Switch Resistance At Vehicle Connector

A. Install 9-Pin Breakout 'T' on Vehicle Connector (J7/P7).

B. Set multimeter on 20,000 ohms (20K) scale and measure the resistance from each switch output terminal (shown in Table A). Operate the Parking Brake Switch and measure the resistance with swith "ON" and with switch "OFF".

The resistance should be as shown in Table A.

OK: Vehicle wiring checks good. Continue to next step.

NOT OK: There is a problem in the vehicle wiring. Repair as needed using the OEM wiring schematics or refer to the OEM Dealer. Stop.

Step 3. Check Switch Resistance At ECM

A. Reconnect the Vehicle Connector (J7 to P7).

B. Install the 40-Pin Breakout 'T' on the ECM Connector, P4 ONLY (not J4).

C. Set multimeter on 20,000 ohms (20K) scale and measure the resistance from each switch output terminal (shown in Table B) to both: - Battery (P4, Pin 12) and to the cylinder head ground stud. Operate each switch and measure the resistance with switch "ON" and with switch "OFF".

The resistance should be as shown in Table B.

OK: The 3176 Wiring harness checks good. If Step 1 found that the ECM is not seeing the switch status change, then the ECM is getting the correct signals, but is not reading them correctly. Check that the ECM is receiving correct battery voltage. If so, replace the ECM. Stop.

NOT OK: There is a problem in the 3176 Wiring harness or the connectors between the vehicle connector and the ECM. Repair as needed. Stop.

P-220: ECM/Personality Module Test

The Electronic Control Module (ECM) is the computer which controls a 3176 Engine. The Personality Module is the software which controls how the computer behaves. The two must be used together - neither can do anything by itself.

The Personality Module consists of:

* All of the software, or instructions, for the ECM to do its job. Because of this, updating the Personality Module to a new version may cause some engine functions to behave in a different manner.

* Performance Maps, which define fuel rate, timing, etc. for various operating conditions to achieve optimum performance while meeting emissions requirements. These are programmed at the factory only.

The ECM consists of:

* A microprocessor, to perform the computing necessary to perform the ECM's functions (governing, controlling timing, generating diagnostic codes, communicating with service tools, etc.). The microprocessor gets its instructions from the software in the Personality Module.

* Programmable Parameters stored in permanent memory (both Customer Specified and System Configuration Parameters). Refer to the section Programming 3176 Parameters for details on what these parameters do.

* Logged Diagnostics, the 3176 System may log certain Diagnostic Codes into this memory so that a permanent record of the Diagnostic Code is retained. Refer to the section Troubleshooting Diagnostic Codes, for further information on logged codes.

* Input Circuits, to filter electrical noise from sensor signals and to protect sensitive internal circuits from potentially damaging voltage levels.

* Output Circuits, to provide the high currents necessary to energize lamps or injector solenoids as the microprocessor chooses.

* Power circuits, to provide clean stable electrical power to internal circuits and external sensors.

Step 1. Inspect Electrical Connectors And Wiring

Inspect the ECM Connector (J4/P4) for damage, corrosion, or incorrect attachment. Repair any problems.

Step 2. Inspect The Personality Module Connector

A. Remove the Personality Module.

B. Inspect the connector on the Personality Module and on the ECM for corrosion or damage.

C. The Personality Module Connector on the ECM should be "stiff" but should be able to be moved by hand.

D. Inspect the O-ring to be certain that it was aligned correctly when installed.

E. Re-install, replace or repair the module, as needed.

Step 3. Check Communication With ECAP or DDT

A. Install ECAP or DDT.

B. With the Personality Module installed on the ECM, turn key ON (engine off).

C. Read Customer Specified Parameters (see instructions for the service tool for details).

D. Read LOGGED Diagnostic Codes.

E. Start the engine.

The ECAP/DDT should be able to read correct parameters, the hour meter for logged codes should represent approximate operating time for the ECM and the engine should start and run normally.

OK: The Personality Module is OK. The microprocessor in the ECM is able to function correctly and read the memory in the ECM and Personality Module. The remainder of the ECM (input circuits, output circuits, and sensor supply voltage circuits) are to be tested individually. If operational problems persist, refer to the procedure in this manual best describing the symptoms. Stop.

NOT OK: If the ECAP/DDT will not communicate with the ECM, refer to P-120: ECAP/DDT will Not Communicate With 3176 System.

* If the Customer Specified Parameters are not as expected, reprogram the parameters. Completely scrambled parameters could mean the ECM is defective.

* If the hour meter for logged codes is scrambled or stuck at zero, or the logged codes are completely scrambled, the ECM may be defective.

* If the engine will not start, refer to P-102: Engine Cranks But Will Not Start.

P-221: Engine Speed/Timing Signal Test

The 3176 Engine Speed/Timing Sensor provides pulse signals to the Electronic Control Module (ECM). The signals are created as the timing reference ring, mounted on the front of the camshaft drive gear, rotates past the pickup (slip head) of the Speed/Timing Sensor. A unique tooth pattern on the timing reference ring allows the ECM to determine crankshaft position as well as engine rpm.

The sensor generates a pulse to the ECM as each tooth passes. The ECM counts the pulses to determine rpm, memorizes the pattern of the pulses and compares that pattern to a standard, in order to determine crankshaft position. Having located #1 cylinder, the ECM then triggers each unit injector in the correct firing order and at the correct time. The actual timing and duration of each injection is determined by the ECM according to engine rpm and load.

The Speed/Timing Sensor receives 13.8 volts DC, regulated and supplied by the ECM. It is not "battery voltage"; it is generated within the ECM and is held within ± 0.5 volts DC. Power is supplied to the sensor at Pin A (+ V Timing) of the Speed/Timing Sensor Connector (J9/P9) and is grounded through the Timing Return, Pin B (J9/P9). The sensor signal goes to the ECM through Pin C of the Speed/Timing Connector (J9/P9).

Step 1. Inspect Connectors, Wiring And Sensor

Check ECM Connector (J4/P4) and Speed/Timing Sensor Connector (J9/P9) and wiring between them, being sure to:

* Check Connector lock rings.

* Perform 10 pound pull test on each pin or wire.

* Inspect wiring for damage or abrasion.

* Inspect connectors for damage or corrosion. Refer to P-201: Inspecting Electrical Connectors for details. Repair any damage, then continue.

Step 2. Inspect Speed/Timing Sensor

A. Remove the Speed/Timing Sensor and inspect the sensor and the black plastic slip-head for damage.

B. Check the tension on the slip head by gently prying it out (about 3/16 ths inch) then pushing it back in. It should take at least five pounds of force to push in the slip head from the extended position

If the sensor or slip head is damaged or the slip head has insufficient tension, replace the sensor. After installation, calibrate the Speed/Timing Sensor, using P-301, Engine Speed/Timing Sensor Calibration, in this manual.

Step 3. Check Display On ECAP/DDT

A. Install the ECAP/DDT on the engine.

NOTE: Since vehicle battery voltage may drop below operating minimum for the ECAP during cranking, electrical power must be supplied from an external isolated source (such as a battery cart) for this step.

B. If possible start the engine. If engine will not start, crank the engine while observing the display on the ECAP/DDT.

C. Check engine rpm on the ECAP/DDT display.

"Engine RPM" while cranking should show a steady reading between 100 and 500 rpm. The engine should start and run and engine rpm should be correct and steady on the ECAP/DDT.

OK: The Speed/Timing Sensor is operating normally. Stop.

NOT OK: If no rpm signal appears on the ECAP/DDT screen, then the ECM is not receiving a good speed/timing signal. Continue with next step.

If the engine will not start, but an rpm signal is displayed on the ECAP/DDT while cranking the engine, the ECM is receiving and processing the speed/timing signal correctly. Refer to P-102, Engine Cranks But Will Not Start, to determine why the engine will not start.

Step 4. Check Supply Voltage At Sensor

A. With key in the OFF position, install the 3-Pin Breakout 'T' on the Speed/Timing Sensor Connector, J9 (ECM side) only. Do not connect to P9 (sensor side) at this time.

B. Turn key ON (engine off).

C. Measure voltage between + V Timing (J9, Pin A) and Timing Return (J9, Pin B) on the Breakout 'T'.

D. After measuring voltage at J9, connect P9 to the Breakout 'T' also.

Voltage should be 13.8 ± 0.5 volts DC.

OK: Supply voltage is reaching sensor. Proceed to Step 7.

NOT OK: Supply voltage is not reaching sensor. Continue to next step.

Step 5. Check Supply Voltage At ECM

A. With key OFF, install a 40-Pin Breakout 'T' at ECM Connector (J4/P4).

B. Turn key ON (engine off).

C. Measure the voltage between + V Timing (J4, Pin 24) and Timing Return (J4, Pin 40) on the 'T'.

The voltage should be 13.8 ± 0.5 volts DC.

OK: The ECM is supplying the correct voltage, but it is not reaching the sensor connector. Check for broken connection in the harness or connectors between the ECM and the sensor. Stop.

NOT OK: The ECM is not supplying correct voltage, or it is shorting to ground in the harness between the ECM and the sensor. Verify that correct battery voltage is reaching the ECM. If so, continue to next step.

Step 6. Check For Short Circuits In Harness

A. With the key OFF, disconnect the 40-Pin ECM Connector (J4/P4).

B. Install the 3-Pin Breakout 'T' on the Speed/Timing Sensor Connection (J9) ONLY. Do not connect P9.

C. Set ohmmeter on 20,000 ohms (20K scale) and measure resistance between +V Timing (J9, Pin A) and Timing Return (J9, Pin B) on the 3-Pin Breakout 'T'.

Resistance should be more than 20,000 ohms (20K).

OK: The supply wire is not shorted to the return wire. If Step 4 found that the supply voltage was not reaching the Speed/Timing Sensor, then the ECM is not supplying the correct voltage. Replace the ECM and calibrate the Boost Pressure and Speed/Timing Sensors. Stop.

NOT OK: There is a short circuit between the supply wire and ground between the Speed/Timing Sensor (J9/P9) and the ECM (J4/P4). Repair the harness as needed. Stop.

Step 7. Check Speed/Timing Signal Voltage At Sensor

A. Remove the signal wire from the harness side of the Speed/Timing Sensor Connector (J9, Pin C) to isolate the harness from the sensor output signal.

B. While cranking the engine, measure the voltage between the Speed/Timing Sensor signal (P9, Pin C) and Timing Return (Pin B) on the 3-Pin Breakout 'T'.

With the key ON, before cranking the engine, the voltage should be less than 2.0 or more than 10.0 volts DC. While cranking the engine, the voltage may vary but should be between 3.0 and 9.0 volts DC.

C. After measuring voltage, re-insert wire into J9, Pin C.

OK: The sensor is producing an output signal. Continue to next step.

NOT OK: The Speed/Timing Sensor is not producing the correct signal. Replace and calibrate the Speed/Timing Sensor. Stop.

Step 8. Check Sensor Output Signal At ECM

A. Install the 40-Pin Breakout 'T' at the ECM Connector (J4/P4).

B. Remove the wire from the Speed/Timing Sensor input (P4, Pin 28) and connect the voltmeter positive lead to the wire.

C. While cranking the engine, measure the voltage between the Speed/Timing Sensor input (P4, Pin 28) and the Timing Return (Pin 40) on the 40-Pin Breakout 'T'.

D. After measuring voltage, re-insert wire into Speed/Timing Sensor input (P4, Pin 28).

With the key ON, before cranking the engine, the voltage should be less than 2.0 or more than 10.0 volts DC. While cranking the engine, the voltage may vary but should be between 3.0 and 9.0 volts DC.

OK: The ECM is receiving the Speed/Timing Sensor Signal. If Step 3 found that the ECM was not processing the Speed/Timing Signal, then the ECM is defective. Replace the ECM and calibrate the Boost Pressure Sensor and the Speed/Timing Sensor using the procedures in this manual.

NOT OK: The Speed/Timing Sensor Signal is not reaching the ECM. Check wiring harness between sensor and ECM for a short or open circuit. Stop.

P-222: Isolating Misfiring Cylinders

The 3176 Diesel Truck Engine utilizes electronic unit injectors which can be individually cut out to aid in troubleshooting misfire problems. This procedure uses that feature to isolate a misfire to a specific cylinder.

Under certain conditions the 3176 Diesel Truck Engine may intentionally operate on only three cylinders. This feature is called "Three Cylinder Cutout" and occurs when the truck is operating at higher rpm under low or no load conditions (when signals to the unit injectors are of very short duration). During "Three Cylinder Cutout" operation, in order to obtain more precise fuel metering in cylinders #1, #2 and #3, the ECM does not signal fuel injection into cylinders #4, #5 and #6. When more power is needed, all six cylinders are fueled and full power is delivered by the engine. The change in feel and sound during "cutout" operation is normal, but may be misdiagnosed as an engine problem.

Step 1. Verify That Complaint Is Not About Three Cylinder Cutout Feature

A. Interview driver to determine conditions when misfire occurs. Also try to determine if driver understands the operation of the three cylinder cutout feature. If the misfire occurs only at higher rpm (1,500 to 1,700 rpm and above), the complaint may be about normal operation of the three cylinder cutout feature.

B. To demonstrate three cylinder cutout, install the Timing Adapter Group on the ECAP (install only injection signal adapter, not timing probe). Install the ECAP on the 3176 System. Run the engine up to high idle while observing the injection duration bar graphs. When the three-cylinder cutout feature is active, the bar graphs for cylinders #4, #5 and #6 should go to zero. The "display status" screens on the ECAP also show a message in the upper corner of the screen when three cylinder cutout is active.

NOTE: Parasitic loads on the engine may prevent the three cylinder cutout from operating.

Step 2. Cut Out Individual Cylinders

A. Install ECAP on engine.

B. Recreate the conditions that existed at the time the problem occurred.

NOTE: If the problem occurs only when the engine is under load, it will be necessary to load the engine using a dynamometer or road test. Misfires occurring only under load should not be diagnosed at idle.

C. Use the "Interactive Diagnostics" Screen on the ECAP to cut out each cylinder, one at a time during the test.

D. Check for a difference in sound, feel or power of the engine as each cylinder is cut out. The amount of change in sound, feel or power of the engine should be about the same for each cylinder.

OK: All cylinders appear to be functioning correctly. Continue to next step.

NOT OK: A specific cylinder is malfunctioning (either weak or dead). Refer to P-223, Injection Subsystem Test On A Specific Cylinder, to determine the cause of the malfunction on that cylinder.

Step 3. Check Injection Signal Duration

A. Install the Timing Adapter Tool Group on the ECAP (install only the adapter for injector signals - there is no need to install the timing probe in the block).

B. Repeat Step 2 while observing the injection duration bar graphs on the ECAP.

As each cylinder is cut out, the duration bar graphs of the remaining cylinders should INCREASE slightly to compensate for the cylinder that was cut out.

OK: All cylinders appear to be functioning correctly. Stop.

NOT OK:

* If a specific cylinder is malfunctioning. Refer to P-223, Injection Subsystem Test On A Specific Cylinder.

* If a problem persists but cannot be assigned to a specific cylinder, Refer to P-103, Engine Misfires, Runs Rough, Or Is Unstable.

P-223: Injection Subsystem Test On A Specific Cylinder

The 3176 Diesel Truck Engine uses electronic unit injectors which are mechanically actuated and electrically energized. During operation, the Electronic Control Module (ECM) sends a 100 volt DC pulse to each injector solenoid. The solenoid operation controls the amount of fuel injected into the cylinders. The ECM determines that fuel is injected at the correct time and for the correct duration, for a given engine load and speed.

This test should be used to determine the cause of a cylinder malfunction, once the malfunctioning cylinder has been identified using P-222: Isolating Misfiring Cylinders.

Step 1. Isolate Misfiring Cylinder

If the cylinder was identified with an ACTIVE Diagnostic Code, continue with next step.

Use P-222, Isolating Misfiring Cylinders, to isolate and identify the misfiring cylinder(s).

Step 2. Check Engine Harness And Connectors

Inspect ECM Connector (J4/P4) and Injector Connector (J5/P5) for damage or poor connection. Inspect engine wiring harness for damage, corrosion, abrasion or incorrect attachment. Repair any problems.

Step 3. Check Injector Harness Under Valve Cover

A. Remove valve cover for malfunctioning cylinder.

B. Inspect engine wiring harness from Injector Connector (J5) to the terminals on top of the fuel injection solenoids for damage, corrosion, abrasion or incorrect attachment (loose terminals). Wires should not be pinched, worn or under tension. Repair any problems.

Step 4. Check Injector Solenoid Resistance

A. Use an ohmmeter, set on the 200 ohm scale, to measure the resistance between the two solenoid terminals on top of the injector.

Resistance between solenoid terminals should be between three and six ohms (nominal 4.5 ohms).

B. Use an ohmmeter, set on the 20,000 ohm (20K) scale, to measure the resistance between either of the solenoid terminals and the injector solenoid case.

Resistance from either solenoid terminal to the injector solenoid case, should be at least 20,000 ohms (20K).

OK: All resistance readings are within limits. The injector is functioning electrically. Continue to next step.

NOT OK: The injector solenoid has failed. Replace the defective injector. Stop.

NOTE: Before removing a unit injector, drain the fuel supply manifold. Refer to 3176 Diesel Truck Engine, Form SENR3914, for Disassembly And Assembly.

Step 5. Check Injector Lash and Valve Lash

Refer to 3176 Diesel Truck Engine, Form No. SENR3909, for Systems Operation, Testing & Adjusting and check the Unit Injector Adjustment and the engine Valve Clearance Setting.

OK: Injector rocker arm and valve clearances are set correctly. If P-222, Isolating Misfiring Cylinders, confirmed that this cylinder is misfiring, then continue to next step. Otherwise, cylinder is functioning correctly. Stop.

NOT OK: A problem is found with the adjustment of the injector rocker arm and/or valve clearance setting. Adjust and/or repair as needed. Stop.

Step 6. Bench Test Unit Injectors

Refer to Special Instruction, Form No. SEHS8867, Using The 1U6661 "Pop" (Injector) Tester to bench test a unit injector.

NOTE: The Pop (Injector) Tester can check the function of unit injector components and spray patterns. It cannot test (simulate) actual operation, because during engine operation, the pulse duration of the unit injector is very short. Therefore, problems associated with low fuel flow rates, such as unstable idle, may not show up during static testing. If the unit "tests" good, but the problem continues to occur in operation, replace the injector.

Step 7. Check For Mechanical Failure

Inspect the cylinder and valve linkage for mechanical damage or failure. Refer to 3176 Diesel Truck Engine, Form No. SENR4248, for Mechanical Troubleshooting, as a guide to locate the source of a mechanical failure.

P-224: Coolant Temperature Sensor Test

The Coolant Temperature Sensor measures the temperature of the engine coolant. The Electronic Control Module (ECM) uses this information to set the mode of engine operation.

Cold Mode is activated whenever coolant temperature is below 17° C (63° F). In Cold Mode, engine power is limited, injection timing is retarded and low idle is increased to approximately 1000 rpm, to improve warm-up time. Once activated, Cold Mode will continue until coolant temperature rises above 28° C (68° F), or until the engine has been running for 12 minutes. The ECM then causes the engine to leave Cold Mode, low idle speed is returned to the rpm set by the Customer Specified Parameters and normal engine operation is restored.

The Coolant Temperature Sensor can measure temperatures from less than -18° C (0° F) to about 65° C (149° F). Above 65° C (149° F), the signal voltage from the sensor goes above 5 volts. Since the ECM is unable to measure voltages above 5 volts, 65° C (149° F) is the maximum temperature that can be measured. The sensor operates on 8.0 volts DC, supplied through Pin 30 of the ECM Connector (J4/P4). The return (ground) line is common with the fuel pressure return line and goes through Pin 35 of the ECM Connector (J4/P4).

Step 1. Inspect Connectors, Wiring And Sensor

Check ECM Connector (J4/P4) and Coolant Temperature Sensor Connector (J10/P10) and wiring between them, being sure to:

* Check Connector lock rings.

* Perform 10 pound pull test on each pin or wire.

* Inspect wiring for damage or abrasion.

* Inspect connectors for damage or corrosion. Refer to P-201: Inspecting Electrical Connectors for details. Repair any damage, then continue with the next step.

Step 2. Compare Temperature Shown On ECAP To Actual Coolant Temperature

A. Install ECAP on the engine.

B. Compare "COOLANT TEMP" shown on the ECAP status display to actual temperature as measured by dash temperature gauge or by using the 6V9130 Temperature Adapter Group installed in the regulator housing.

The two measurements should agree within ± 15° C (± 27° F).

OK: Coolant Temperature Sensor is working correctly. Stop.

NOT OK: There is a problem in the coolant temperature sensing circuit. Continue with next step.

Step 3. Check Supply Voltage To Sensor

A. With key OFF, install the 3-Pin Breakout 'T' on the harness side of the Coolant Temperature Sensor Connector (P10) only. Do not connect to J10 (sensor side) at this time.

B. Turn key ON (engine off).

C. Measure sensor supply voltage between +V Coolant (P10, Pin A) and Coolant Return (P10, Pin B), on the 'T'.

Supply voltage should be 8.0 ± 0.5 volts DC.

OK: Supply voltage is normal. Proceed to Step 6 to check signal voltage from the sensor.

NOT OK: The sensor is not receiving correct supply voltage. Continue to next step.

Step 4. Check Supply Voltage At ECM

A. With the key OFF, install the 40-Pin Breakout 'T' on the ECM Connector (J4/P4).

B. Turn key ON (engine off) and measure sensor supply voltage between +V Fuel Pressure (P4, Pin 10) and Sensor Return Analog (P4, Pin 35) on the 'T'.

Supply voltage should be 8.0 ± 0.5 volts DC.

OK: Supply voltage is present at the ECM but not at the sensor. Repair fault in harness between ECM and Coolant Temperature Sensor. Stop.

NOT OK: The ECM is not supplying correct voltage or there is a short to ground in the harness between the ECM and the sensor. Verify that the ECM is receiving correct voltage from the battery. If it is, continue to the next step.

Step 5. Check For Shorts In Wiring Harness

A. With the key OFF, disconnect the ECM Connector (J4/P4).

B. Install the 3-Pin Breakout 'T' on the Coolant Temperature Sensor Connector (P10) (harness side) ONLY. Do not connect to J10 at this time.

C. Set multimeter on the 20,000 ohm (20K) scale and measure resistance between +V Coolant (P10, Pin A) and Coolant Return (P10, Pin B) on the 3-Pin Breakout 'T'.

Resistance should be more than 20,000 ohms.

OK: The voltage supply wire is not shorted to the return wire. If Step 4 found the supply voltage incorrect at the ECM, then the ECM is defective. Replace the ECM. Stop.

NOT OK: The voltage supply to the Coolant Temperature Sensor is being shorted to ground. The return wire for the Coolant Temperature Sensor is common with the Fuel Pressure Sensor. Disconnecting J16/P16 will isolate the Fuel Pressure Sensor. If a short is still present, check connectors and harness between the ECM and the Coolant Temperature Sensor. Stop.

Step 6. Check Signal Voltage At Sensor

A. Install thermocouple probe into the water temperature regulator housing. Use the instructions with the adapter group to determine the correct probe length for an accurate reading.

B. With the key OFF, install the 3-Pin Breakout 'T' on the Coolant Temperature Sensor Connector (J10/P10).

C. Turn key ON (engine off) and measure sensor signal voltage between Coolant (J10, Pin C) and Coolant Return (J10, Pin B) of the 3-Pin Breakout 'T'.

D. Use Table A in this procedure to determine coolant temperature from sensor voltage readings. Compare temperature found in Table A with temperature shown on the Temperature Adapter Group.

The temperature from Table A should agree within 10° C (18° F) with the temperature reading from the adapter group.

OK: Voltage is correct for observed temperature. Continue to next step.

NOT OK: Voltage is incorrect for observed temperature or signal is not present. Replace Coolant Temperature Sensor.

Step 7. Check Signal Through Harness To ECM

A. With key OFF install the 40-Pin Breakout 'T' at the ECM Connector (J4/P4).

B. Turn key ON (engine off) and measure sensor signal voltage between Coolant (Pin 20) and Sensor Return Analog (Pin 35) on the Breakout 'T'.

C. Use Table A of this procedure to determine coolant temperature from sensor voltage readings. Compare temperature found in Table A with temperature shown on the Temperature Adapter Group. The temperature from Table A should agree within 10° C (18° F) with the temperature from the adapter group.

OK: The signal is reaching the ECM. If Step 2 found that the ECM is not reading the correct temperature, then the ECM is defective. Replace the ECM. Stop.

NOT OK: The signal is not reaching the ECM. Check and repair the wiring harness between the Coolant Temperature Sensor and the ECM. Stop.

P-225: Boost Pressure Sensor Test

The 3176 System monitors boost pressure with a sensor located inside the Transducer Module. The Boost Pressure Sensor is supplied with electrical power from the ECM, through the Boost Sensor Connector (inside the module) to + V Boost (Pin 1). The signal voltage is on Boost (Pin 2) and Sensor Return is on Return (Pin 3).

The Boost Pressure Sensor is used to limit smoke emissions during acceleration. The ECM limits the amount of fuel injected until certain boost pressures are reached. It does this by converting boost pressure to "FRC Fuel Pos." (as shown on the ECAP status display). The "FRC Fuel Pos." is an electronic limit on the amount of fuel injected and is based on a ratio of fuel to air being supplied to the cylinders. It operates in a manner similar to the fuel ratio control on an engine with a mechanical governor.

Step 1. Visual Inspection

A. Check that boost and air filter hoses are installed correctly.

B. Remove the boost pressure hose from the Transducer Module and inspect the hose and fittings for cracks, breaks or other damage. Repair as necessary.

Step 2. Check For Moisture In Hoses And Transducer Module

A. Check for moisture inside the transducer end of the boost pressure hose.

B. Check the Transducer Module boost hose fitting for the presence or evidence of water entry into the module.

There should be no evidence of moisture entry in the boost hose or in the Transducer Module.

OK: Continue to next step.

NOT OK: Condensation may be causing moisture in the boost pressure hose. Inspect the intake manifold end of the hose for correct fitting and repair. Then proceed to Step 6, to determine if further damage was done by the moisture entry.

Step 3. Calibrate Boost Sensor

Refer to procedure P-302: Boost Pressure Sensor Calibration to calibrate the boost sensor.

The ECAP or DDT should indicate that the Boost Pressure Sensor was calibrated.

OK: Continue to next step.

NOT OK: Boost Pressure Sensor voltages are not within specified range. Proceed to Step 6.

Step 4. Boost Sensor Pressure Test

A. Disconnect the boost pressure and inlet air pressure lines from the Transducer Module.

B. Connect the FT1906 Fuel Ratio Control Pressure Test Kit to the boost pressure port on the Transducer Module.

C. Observe the boost pressure display on the ECAP or DDT's Display Status Screen.

D. Close the pressure cock valve on the pressure test kit and apply 100 kPa (14.5 psi) to the boost pressure port.

E. Compare the readings on the ECAP or DDT with the pressure test kit.

The ECAP or DDT should show 0 kPa when no pressure is applied and should agree within ± 7 kPa (1.0 psi) of the test kit when pressure is applied.

OK: Boost sensor appears to operate normally. Continue to next step.

NOT OK: The ECM is not reading a correct signal from the Boost Pressure Sensor. Proceed to Step 6.

Step 5. Leakage Test

A. Close the pressure cock valve on the pressure test kit and again apply 100 kPa (14.5 psi) to the boost pressure port.

B. Observe the boost pressure reading on the ECAP or DDT for 30 seconds before releasing the pressure.

The leakage rate should not exceed 8 kPa (1.1 psi) in 30 seconds.

OK: The Boost Pressure Sensor and Transducer Module are currently operating correctly. Stop.

NOT OK: Check for leaks in the hose or the test kit. If none are found, there is an internal leak in the Transducer Module. Replace the Transducer Module. Stop.

Step 6. Inspect Transducer Module And 5-Pin Connector

A. Disassemble the Transducer Module from the ECM and disconnect the 5-Pin Connector inside it (the ECM normally has only three wires to this connector).

B. Inspect the inside of the Transducer Module and the 5-Pin Connector to be certain there is no corrosion or damage.

OK: The module and connector are not damaged or corroded. Continue to next step.

NOT OK: There are signs of moisture, damage or corrosion. Repair damage if possible, otherwise replace the Transducer Module and calibrate the Boost Pressure Sensor. Stop.

Step 7. Check Supply Voltage From ECM

A. Install the 5-Pin Transducer Module Breakout 'T' to the socket from the ECM. Leave it DISCONNECTED from the 5-Pin Connector located inside the Transducer Module.

B. Turn key ON (engine off).

C. Measure the voltage from +V Boost (Pin 1) to Return (Pin 3) of the 'T' Connector.

The voltage should be 8.0 ± 0.5 volts DC.

OK: Supply voltage is reaching the sensor. Continue to next step.

NOT OK: The sensor voltage is not being supplied by the ECM. Replace the ECM. Stop.

Step 8. Check Boost Sensor Signal Voltage

A. Connect the 5-Pin Transducer Module Breakout 'T' to both the ECM and the Transducer Module.

B. With the key ON (engine off), measure the voltage from Boost (Pin 2) to Return (Pin 3).

The voltage should be 1.0 ± 0.15 volts DC at atmospheric pressure.

OK: The Boost Pressure Sensor is working correctly. If Step 4 found that the ECM was not reading a correct boost pressure reading, then the ECM is defective. Replace the ECM. Stop.

NOT OK: The Boost Pressure Sensor is not generating a good signal. Replace the Transducer Module. Stop.

P-226: Fuel Pressure Sensor Test

The 3176 System monitors fuel pressure with a sensor located at the top of the fuel filter housing. The Fuel Pressure Sensor is supplied with 5.0 volts DC through the ECM Connector (J4/P4, Pin 10). The sensor return line goes through the ECM Connector (J4/P4, Pin 35) which is common with the Coolant Temperature Sensor. The Fuel Pressure Signal goes to the ECM Connector (J4/P4, Pin 39).

Fuel pressure is regulated to a maximum of approximately 550 kPa (80 psi).

Step 1. Inspect Connectors And Wiring

Inspect the Fuel Pressure Sensor Connector (J16/P16) and the ECM Connector (J4/P4) and wiring between being sure to:

* Check Connector lock rings.

* Perform 10 pound pull test on each pin or wire.

* Inspect wiring for damage or abrasion.

* Inspect connectors for damage or corrosion. Refer to P-201: Inspecting Electrical Connectors for details. Repair any damage, then continue with the next step.

Step 2. Check Actual Pressure With Gauge

A. Install the 8T0846 Pressure Gauge (0 to 145 psi)(part of 1U5470 Pressure Group) on a "T" fitting with the Fuel Pressure Sensor.

B. Start the engine and monitor the fuel pressure at low idle.

C. Operate the engine at high idle and check the fuel pressure.

Fuel pressure at low idle should be greater than 300 kPa (43.5 psi), and at high idle should be 550 ± 85 kPa (80 ± 12 psi) and remain steady.

OK: Fuel pressure is within normal limits. Continue to next step.

NOT OK: Fuel pressure is outside normal limits, is erratic or leakage is present. The problem is NOT in the 3176 Electronic Control System. Refer to 3176 Diesel Truck Engine, Form No. SENR3909, for Systems Operation, Testing & Adjusting, or 3176 Diesel Truck Engine, Form No. SENR4248, for Mechanical Troubleshooting, for help in identifying and repairing the cause of the problem. Stop.

Step 3. Compare Actual Pressure With ECAP/DDT

A. With key OFF, install ECAP/DDT on the 3176 System.

B. Start the engine and run at low idle. Compare the fuel pressure gauge reading with the display on the ECAP or DDT and record.

C. Operate the engine at high idle. Compare the gauge reading with the display on the ECAP or DDT and record.

The ECAP/DDT display should be steady and within ± 40 kPa (6 psi) of the gauge readings.

OK: The Fuel Pressure Sensor is operating correctly. Stop.

NOT OK: The ECM is not reading fuel pressure correctly. Continue to next step.

Step 4. Check Supply Voltage To Sensor

A. With key OFF, install the 3-Pin Breakout 'T' on the Fuel Pressure Wiring Connector (J16) ONLY. Do not connect to the Fuel Pressure Sensor Connector (P16) at this time.

B. Turn key ON (engine off).

C. Use the multimeter to measure the voltage between + V, Pin A (J16) and Return, Pin B on the 3-Pin Breakout 'T'.

The voltage should be 5.0 ± 0.5 volts DC.

OK: The Fuel Pressure Sensor is receiving the correct voltage. Proceed to Step 7.

NOT OK: Supply voltage is not reaching the sensor. Continue to next step.

Step 5. Check Supply Voltage At ECM

A. With the key OFF, install the 40-Pin Breakout 'T' on the ECM Connector (J4/P4).

B. Turn key ON (engine off), and use the multimeter to measure the sensor supply voltage between +V Fuel Press., Pin 10 (J4/P4) and Sensor Return (P4, Pin 35) on the 'T'.

The voltage should be 5.0 ± 0.5 volts DC.

OK: Supply voltage is present at the ECM but not at the sensor. Repair fault in harness between ECM and Fuel Pressure Sensor. Stop.

NOT OK: The ECM is not supplying the correct voltage or it is being shorted in the harness between the ECM and the sensor. Verify that the ECM is being supplied with battery voltage. If so, continue to next step.

Step 6. Check For Shorts In Wiring Harness

A. With key OFF, disconnect the 40-Pin ECM Connector (J4/P4)

B. Install the 3-Pin Breakout 'T' on the Fuel Pressure Wiring Connector (J16) ONLY. Do not connect to the Fuel Pressure Sensor Connector (P16) at this time.

C. Set the multimeter on the 20K (20,000 ohm) scale and measure resistance between + V, Pin A (J16) and Press. Return, Pin B (J16) on the 3-Pin Breakout 'T'.

Resistance should be more than 20,000 ohms.

OK: The voltage supply wire is not shorted to the return wire. If Step 5 found an incorrect supply voltage at the ECM, then the ECM is defective. Replace the ECM. Stop.

NOT OK: The voltage supply to the sensor is being shorted to ground. Check connectors and the wiring harness between the ECM and the Fuel Pressure Sensor. Stop.

Step 7. Check Signal Output At Sensor

A. Connect the 3-Pin Breakout 'T' to the Fuel Pressure Sensor Connector (J16/P16).

B. Remove Wire C (fuel press) from J16 (harness side) of connector.

C. Start the engine.

D. Measure the voltage between the Fuel Pressure Signal (Pin C) and the Pressure Return (Pin B) on the Breakout 'T'.

E. After measuring the voltage, reinstall Wire C into the connector.

The signal voltage reading should correspond to the observed fuel pressure reading shown in Table A.

OK: The Fuel Pressure Sensor is operating correctly. Continue to next step.

NOT OK: The Fuel Pressure Sensor is receiving the correct supply voltage, but is not generating the correct signal voltage. Replace the Fuel Pressure Sensor. Stop.

Step 8. Check Signal Voltage At ECM

A. Install the 40-Pin Breakout 'T' at the ECM Connector (J4/P4).

B. Measure the voltage between Fuel Pressure, Pin 39 and Sensor Return Analog, Pin 35.

The signal voltage should correspond to the observed fuel pressure reading shown in Table A.

OK: The Fuel Pressure Signal is reaching the ECM. If Step 3 found that the ECM is not reading fuel pressure correctly, then the ECM is defective. Replace the ECM. Stop.

NOT OK: The signal was good at the sensor but did not reach the ECM. Repair the wiring harness between Fuel Pressure Sensor and the ECM. Stop.

P227: Retarder Enable Signal Test

The "Retarder Enable" signal is provided by the ECM to indicate that conditions are acceptable for an engine retarder to operate. Operation of the retarder is inhibited during undesirable engine operating conditions (such as while the engine is being fueled).

With the Cruise Control ON/OFF Switch in the OFF position, the retarder is enabled under the following conditions:

* engine rpm is greater than 950 rpm and

* driver's foot is off the throttle pedal and the clutch pedal

With the Cruise Control ON/OFF Switch "ON", the operation of the retarder is also controlled through the customer parameter "Engine Retarder Mode". Programming the parameter to "COAST" allows retarding with the service brakes applied, but allows the engine to coast with no retarding after they are released. Programming the parameter to "LATCH" allows retarding with the service brake applied and keeps the retarder latched on after the service brakes are released (until engine rpm drops below 950 rpm or the driver presses the throttle or clutch pedal).

The Retarder Enable Signal should be 15% Duty Cycle (nominal) to indicate that the retarder is enabled and 85% Duty Cycle (nominal) to indicate that it is disabled. The remainder of the engine retarder circuit is supplied by the OEM. In typical installations, the Retarder Enable signal isused by a separate Brake Control Module, which then energize the retarder solenoids. An "Engine Brake On" Switch is also typically connected to the Brake Control Module, and must be ON before the brake will operate.

Step 1. Inspect Connectors And Wiring Harness

Inspect the Vehicle Connector (J7/P7) and the ECM Connector (J4/P4) connections and wiring between, being sure to:

* Check Connector lock rings.

* Perform 10 pound pull test on each pin or wire.

* Inspect wiring for damage or abrasion.

* Inspect connectors for damage or corrosion. Refer to P-201: Inspecting Electrical Connectors for details. Repair any damage, then continue with the next step.

Step 2. Verify Throttle Position And Clutch Switch Inputs

A. Use P-303: Throttle Position Sensor Adjustment procedure to verify correct adjustment of the throttle pedal.

NOTE: The "Throttle Position Signal" must be less than 7% at low idle, to perform the remainder of this test procedure.

B. Use P-215: Service Brake And Clutch Switch Test, to verify correct adjustment and operation of the Clutch Pedal Switch.

NOTE: Clutch Switch Status must be OFF, with foot off the clutch, to perform the remainder of this test procedure.

Step 3. Check Retarder Enable Signal At Vehicle Connector During Deceleration

A. With the key OFF, install the 9-Pin Breakout 'T' to the Power/Data Link Connector (J8/P8).

B. Install PWM Adapter Group to ECAP/DDT and put PWM Probe into J8/P8 Pin C on the 'T'.

C. Start the engine.

D. Turn the Cruise Control ON/OFF switch to the "OFF" position.

E. Shift transmission into neutral and leave foot off clutch pedal.

F. Increase engine speed to high idle by depressing the throttle pedal to the maximum position.

G. At high idle, measure the Duty Cycle between Retarder Enable (Pin C) and ground (Pin B) on the Breakout 'T'.

H. Release the throttle pedal completely and measure the voltage while the engine is decelerating from high idle to 950 rpm.

The Duty Cycle should remain at 80% to 90% with the engine held steady at high idle. The Duty Cycle should change to 10% to 20% while the engine is decelerating from high idle to 950 rpm. (Below 950 rpm the retarder is disabled).

OK: The Retarder Enable output is correct. Stop.

NOT OK: The Retarder Enable output is not correct. Continue to next step.

NOTE: If engine deceleration occurs too quickly (less than 1.5 seconds) the Retarder Enable Status CANNOT be measured accurately while the vehicle is stationary. Status should then be measured during a road test of the vehicle.

Step 4. Check Retarder Enable Signal At ECM During Deceleration

A. With the key OFF, install the 40-Pin Breakout 'T' at the ECM Connector (J4/P4).

B. Install PWM Probe on J4/P4 Pin 14 on the 'T'.

C. Repeat Step 3 of this procedure, measuring the Duty Cycle between Retarder Enable (Pin 14) and Ground (Pin 21) on the Breakout 'T'.

The Duty Cycle should remain at 80% to 90% with the engine held steady at high idle. The Duty Cycle should change to 10% to 20% while the engine is decelerating from high idle to 950 rpm.

OK: The ECM is generating the correct Retarder Enable Signal, but the signal is not getting to the Power/Data Link Connector (J8/P8). Repair the wiring harness between the ECM Connector (J4/P4) and the Power/Data Link Connector (J8/P8). Stop.

NOT OK: The ECM is not generating the correct Retarder Enable Signal. Replace the ECM. Stop.

P-230: Idle Shutdown Timer Test

The Idle Shutdown Timer is a feature which helps improve fuel consumption by limiting idling time. The timer may be programmed to shut down the idling engine after a period of time. This "Shutdown Time" is a Customer Specified Parameter and may be programmed for any period from three to sixty minutes. Programming the time to zero disables the Idle Shutdown Timer.

The timer is activated when the parking brake is set, vehicle speed is zero and the engine is not under load. Ninety (90) seconds before the programmed time is reached the Diagnostic Lamp will begin to flash rapidly. If the driver moves the clutch pedal or brake pedal during this 90 second period, the timer will be overridden until it is reset by releasing then reapplying the parking brake. A Diagnostic Code 01 will be logged when the driver uses the clutch or brake to override the timer.

If the timer is activated and is allowed to shut down the engine, then a Diagnostic Code 47 will be set. Both 01 and 47 merely record the event and do not indicate a fault in the 3176 System.

NOTE: If any of the following codes are ACTIVE, the Idle Shutdown Timer WILL NOT OPERATE:

* Diagnostic Code 31 (Loss of Vehicle Speed Signal)

* Diagnostic Code 36 (Vehicle Speed Signal Out of Range)

* Diagnostic Code 57 (Parking Brake Fault)

Follow the procedure indicated under the affected Diagnostic Code and correct that problem before attempting to test the Idle Shutdown Timer.

NOTE: The engine must be out of Cold Mode for the Idle Shutdown Timer to operate.

Step 1. Verify Activation Of Idle Shutdown Timer

A. Install the ECAP/DDT.

B. Record the programmed Idle Shutdown Time. It must be between 3 and 60 minutes (If programmed to 0, timer is disabled).

C. Start the engine and verify that it is not in Cold Mode.

D. Set the parking brake.

E. Observe "Idle Shutdown" status on the ECAP or DDT.

With vehicle not moving and no load on the engine, "Idle Shutdown" status should change from "NOT ACTIVE" to "COUNTING".

OK: The ECM is seeing the correct conditions to activate the Idle Shutdown Timer. Continue with next step.

NOT OK: The ECM is not seeing the correct conditions to activate the timer. Check the following:

P-216: Parking Brake Switch TestP-213: Vehicle Speed Signal Test

The repeat Step 1 of this procedure.

Step 2. Verify Driver Alert Function And Override Function

A. Repeat Step 1 above to activate the idle shutdown timer.

B. Observe the Diagnostic Lamp and the "Idle Shutdown" status during the ninety second period before the programmed shutdown time.

C. During the last ninety seconds, press either the service brake or clutch pedal to override the shutdown.

Ninety seconds before the scheduled shutdown, the Idle Shutdown Status should change from "COUNTING" to "DRIVER ALERT" and the Diagnostic Lamp should begin flashing rapidly. After pressing the service brake or clutch pedal, the status should change to "DISABLED".

OK: The Idle Shutdown Timer is operating normally. Stop.

NOT OK: If the diagnostic lamp is not flashing during the alert, refer to P-212: Diagnostic Lamp Test. If the ECM did not sense a change in clutch or brake status, refer to P-215: Service Brake And Clutch Switches Test. Then repeat this step.