ELECTRONIC TROUBLESHOOTING 3176 DIESEL TRUCK ENGINE Caterpillar

P-301: Engine Speed/Timing Sensor Calibration

The 3176 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. Minor changes in position, relative to the timing reference ring, may occur whenever the sensor is moved or replaced. It then becomes necessary to calibrate the sensor.

Step 1. Install The Timing Adapter Group

A. Turn the engine off at the ignition switch.

Engine - Right Side

Magnetic Pick-up Sensor
(1) Magnetic pick-up sensor. (2) Adapter sleeve for magnetic pick-up.

Timing Adapter Module Installed On ECAP
(3) ECAP. (4) Timing adapter module. (5) Cable for magnetic pick-up.

B. Install the 8C9995 Module Adapter Plate on the ECAP. Install timing adapter module to the module adapter plate. Connect cable for the magnetic pick-up to the timing adapter module.

C. Use the Turning Tool to put either #1 or #6 piston at top-dead-center on the compression stroke.

D. Remove the Timing Calibration Plug from the right side of the cylinder block (on the #4 cylinder rod pocket) and install the Timing Probe Adapter Sleeve into the hole.

Installed Magnetic Pick-up Sensor
(1) Magnetic pick-up sensor. (2) Adapter sleeve for magnetic pick-up. (6) Counterweight. (7) TDC slot. (A) 1.02 mm (.040 in).

E. Rotate the engine until #1 cylinder is between 10 and 90 degrees before-top-dead-center (BTDC). This positions the counterweight surface in front of the timing calibration hole.

NOTE: The counterweight must be a minimum of 10 degrees BTDC to make sure the timing probe is positioned on counterweight surface and not TDC slot.

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If the crankshaft is not in the correct position when the magnetic pickup sensor is installed, the magnetic probe will be damaged when the engine is started.

F. Put a 2D6392 O-Ring Seal on the end of the Magnetic Pick-up Sensor (a small amount of clean engine oil will let the seal slide onto the sensor more easily).

G. Push the sensor through the adapter until it comes in contact with the counterweight and move the O-Ring Seal down against the adapter.

H. Withdraw the sensor 1 mm (.04 in) and hand tighten the nut on the adapter sleeve to firmly hold the timing probe in position.

I. Connect cable for magnetic pick-up to the magnetic pick-up sensor.

Step 2. Install ECAP And Injector Harness

A. Connect an ECAP to the Engine Data Link Connector (J8).

B. Install the Injection 'T' Harness on the Fuel Injector Connector (J5/P5) in the valve cover base.

C. Be certain all connections (probe, harness, ECAP) are made correctly.

NOTE: Use special care when connecting 'T' Harness to J5. The plug can be mis-aligned. Also use care when reconnecting J5 and P5. Incorrect installation will result in a "No Start" condition.

Step 3. Calibrate Speed/Timing Sensor

A. Start the engine and run at low idle until the engine has warmed up enough to change out of Cold Mode operation. If equipped, turn the cruise control ON/OFF switch to the OFF position. The "Diagnostic Lamp" should go out after the engine has started and the 10 second lamp test is complete. The engine rpm will decrease from approximately 1000 rpm while in the cold mode to the programmed low idle rpm when out of Cold Mode.

B. Check for ACTIVE Diagnostic Codes. Use the procedures in this manual to troubleshoot and repair any ACTIVE Diagnostic Codes before attempting a calibration check.

C. After engine has shifted out of Cold Mode, select the 3176 Timing Calibrate Screen on the ECAP.

NOTE: To insure the most accurate timing calibration, the engine rpm should be held as steady as possible at approximately 1500 rpm. This can be performed using the PTO engine governor or a steady foot on the accelerator pedal. Any major changes (greater than 100 rpm) will slow down the procedure and make it less accurate.

D. Press on the "space" key on the ECAP and wait until the ECAP indicates timing is CALIBRATED (approximately 15 seconds).

E. Verify that timing has been calibrated by observing the "Desired Timing" bar display on the ECAP. Run the engine at different rpm's using the throttle or PTO switches if available.

* If the ECAP display reads that injection timing is CALIBRATED, but during verification, the actual timing bar display is not within the two vertical timing tolerance lines and/or the display is erratic, repeat the timing calibration procedure.

* If the ECAP display reads UNABLE TO CALIBRATE TIMING, the electronic injection timing has NOT been set.

OK: Timing is functional and calibrated if the right end of the bar graph display stays within the vertical bars at all steady speeds.

NOT OK: Recheck the tool installation and tool operation. Verify that the engine speeds were kept stable (± 50 rpm) during testing. If engine speed was unstable or could not be controlled within ± 50 rpm because of mechanical or electrical factors, refer to P-103: Engine Misfires, Runs Rough Or Is Unstable.

NOT OK: If all of the above checks are OK but the timing still will not calibrate, refer to P-221: Engine Speed/Timing Signal Test in this manual.

P-302: Boost Pressure Sensor Calibration

The 3176 Boost Pressure Sensor must be calibrated for a zero boost condition with the engine OFF. Calibration is accomplished electronically without need for manual adjustments.

The sensor must be recalibrated whenever the transducer module or ECM has been replaced. Incorrect sensor calibration may result in poor engine response or a Diagnostic Code 25 (Boost Pressure Sensor Fault) or a Diagnostic Code 42 (Check Sensor Calibration).

Calibration Procedure:

1. Start engine and warm up to normal operating temperature, then turn key OFF.

2. Turn key ON (engine off). The sensor will not calibrate if the engine is running.

3. Select the Boost Sensor Calibration screen on the ECAP or DDT (see the Special Instructions included with the ECAP or DDT).

4. Wait several seconds for the automatic calibration to occur. The screen will display "Calibrated" when finished.

5. If the boost pressure sensor will not calibrate, follow P-225: Boost Pressure Sensor Test.

P-303: Throttle Position Sensor Adjustment

The Throttle Position Sensor (TPS) is used to provide a throttle signal to the Electronic Control Module (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. When correctly adjusted, the "Remote Mounted" TPS will produce a "Duty Cycle" signal of 15% to 20% at the low idle throttle position and 80% to 85% at the maximum throttle position. The "Pedal Mounted" TPS will produce a "Duty Cycle" of 10% to 22% at the low idle throttle position and 75% to 90% at the high idle throttle position. This signal is translated by the ECM into a "THROTTLE POSITION" signal of 3% at low idle and 100% at full throttle. Always use "DUTY CYCLE" for sensor adjustment.

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 (explained in this procedure). 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 (this procedure NOT needed). Both sensors provide the same type of signal to the ECM.

Step 1. Inspect Throttle Linkage

Inspect the throttle linkage for loose, bent, broken, missing, or worn components. Also check for interference with the linkage or spring. The throttle linkage should work smoothly without excessive drag and return to a low idle position without assistance in less than 1 second. Repair linkage if needed.

Step 2. Adjust At Low Idle Position

A. With key OFF-

* Install the 40-Pin Breakout 'T' on the Vehicle Connector (J7/P7).

* Connect Pulse Width Modulation Probe (from ECAP/DDT) to the Throttle Signal (Pin 40) of the Breakout 'T'.

NOTE: New Service Program Modules (SPM) allow the "Throttle Duty Cycle" to be read directly from the ECM without using the Pulse Width Modulation Probe. With the new SPM installed on the ECAP, simply select "Calibrate/Monitor Sensors" from the ECAP menu screens, to display the duty cycle as seen by the ECM.

B. Adjust the pedal stop or the throttle linkage until the "DUTY CYCLE" reading shown on the ECAP or DDT is between 15% and 20% with the throttle pedal at low idle. Slight movement of the throttle pedal off the low idle linkage stop should increase the "Duty Cycle" readings.

Correct Low Idle Position Adjustment
(1) Rotary disc. (2) Mechanical stop. (3) Low idle edge indicator. (4) Roll pin.

When correctly adjusted, the rotary disc should be positioned as shown when the pedal is in the low idle position.

Step 3. Adjustment At High Idle Position

A. With the pedal in the maximum throttle position, adjust the pedal stop or the throttle linkage until an 80% to 85% "DUTY CYCLE" is achieved. Slight movement of the throttle pedal off the maximum throttle position should decrease the "DUTY CYCLE" readings.

Correct High Idle Position Adjustment
(1) Rotary disc. (2) Mechanical stop. (3) Low idle edge indicator. (4) Roll pin. (5) High idle edge indicator.

When correctly adjusted, the rotary disc should be positioned as shown when the pedal is in the high idle position.

Step 4. Verify Adjustment

A. Repeat Steps 2 and 3 until correct conditions are met for both.

B. If the TPS can not be correctly adjusted, refer to procedure P-211: Throttle Position Sensor Test.

NOTE: To see 3% and 100% on "THROTTLE POSITION" status display (after adjusting the PWM value), the key must be turned OFF, then back ON. The ECM will automatically calibrate to the new PWM values for low idle and full throttle.

P-304: Vehicle Speed Calibration

The 3176 System uses vehicle speed information for cruise control, to limit engine speed in certain gears, and to limit vehicle speed.

The 3176 System calculates vehicle speed by converting the vehicle speed signal to miles per hour. The conversion factor is customer programmable and is stored in Pulses Per Mile (PPM).

* tire revolutions per mile

* rear axle ratio

* number of chopper teeth on the transmission drive shaft where the magnetic pickup sensor is mounted.

Step 1. Calculating Pulses Per Mile When All The Variables Are Known

To calculate Pulses per Mile:

Pulses Per Mile = (tire revolutions/mile) X (rear axle ratio) X (No. of chopper teeth).

Where:

* Tire revolutions per mile can be found from the following tables. The radii listed are an average of several major tire manufacturers.

If your tire size is not in the tables, you may calculate tire revolutions per mile by using the following formula:

Tire revolutions per mile = 10,085 divided by tire radius (in inches).

* Rear axle ratio can typically be found on the housing of the rear axle, or on the specification sheet for the vehicle.

* No. of chopper teeth is usually 16. (Some transmissions have 11 tooth chopper wheels.

Step 2. Correcting Vehicle Speed Calibration When Some Variables Are Not Known

A. Determine the actual vehicle speed with a chassis dynamometer, or a stop watch, or an accurate speedometer.

B. Divide the speed displayed on the ECAP/DDT by the actual speed, and multiply this answer times the vehicle speed calibration parameter already programmed in the electronic control module (ECM). This is the corrected PPM that should be used for the new parameter.

Example:

ECAP speed = 55 mph

Actual speed = 65 mph

Present PPM = 29836

Correct PPM:

(55 mph ÷ 65 mph) × 29836 PPM = 25246 PPM (corrected)

Program 25246 PPM into the ECM with the ECAP/DDT and the correct speed should now be displayed.

Radial Tire Revolutions Per Mile

Bias Tire Revolutions Per Mile