C4.4 and C6.6 Industrial Engines and Engines for Caterpillar Built Machines Caterpillar

Use this procedure under the following situation:

Use this procedure if any of the following diagnostic codes are indicated:

• 0041-03 8 Volt DC Supply voltage above normal

• 0041-04 8 Volt DC Supply voltage below normal

• 0091-08 Throttle Position Sensor abnormal frequency, pulse width, or period

Also, use this procedure if the digital throttle position sensor is suspected of incorrect operation.

Digital Throttle Position Sensor

The digital throttle position sensor is used to provide a digital throttle position signal to the Engine Control Module (ECM). The sensor output is a constant frequency signal with a pulse width that varies with the throttle position. This output signal is referred to as either a duty cycle or a pulse width modulated signal (PWM) and this output signal is expressed as a percentage between 3 and 100 percent.

The digital throttle position sensor is most likely to be attached directly to the throttle assembly. The digital throttle position sensor requires no adjustment.

The digital throttle position sensor will produce a duty cycle of 10 to 22 percent at low idle and 75 to 90 percent when the throttle pedal is fully depressed. The percent of duty cycle is translated in the ECM into a throttle position of 3 to 100 percent.

The digital throttle position sensor is powered by +8 Volts DC from the ECM. The supply voltage is from the J1:43 to terminal "A" of the digital throttle position sensor connector.

If the application is using the ECM dedicated PTO functions, the digital throttle position sensor will be ignored while the engine is in PTO mode.

The ECM is in PTO mode if the "PTO ON/OFF Switch" is ON. This can be checked with the electronic service tool. Refer to Troubleshooting, "PTO Switch Circuit - Test" for testing if the PTO is being used.

Illustration 1	g01802294
Typical schematic of the digital throttle position sensor

Illustration 2	g01802315
Typical example of the pin locations on connector P1 (33) Sensor return (43) Sensor supply (+8 Volts DC) (53) Sensor input

Test Step 1. Inspect Electrical Connectors and Wiring

1. Inspect the P1/J1 connector, OEM harness and the connectors on the harness. Thoroughly inspect the digital throttle position sensor connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the digital throttle position sensor:
   • P1:33

   • P1:43

   • P1:53

3. Check the screw for the ECM connector for the correct torque of 5.0 N·m (44 lb in).

4. Check the harness for abrasion and pinch points from the digital throttle position sensor to the ECM.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness is free of corrosion, of abrasion or of pinch points.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Perform the following repair:Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect the electronic service tool to the diagnostic connector.

2. Turn the keyswitch to the ON position.

3. Monitor the active diagnostic code screen on the electronic service tool. Check and record active diagnostic codes.

   Note: When the ECM automatically calibrates new duty cycle values for the low idle throttle position and the high idle throttle position, the ECM assumes 22 percent duty cycle at low idle and 75 percent duty cycle at high idle. As a result, you may notice that the throttle position status reaches 100 percent well before the throttle pedal is fully depressed. This is normal. After some cycling of the throttle to the high idle position, the ECM will adjust the calibration automatically, provided that the high idle stop position is within the 75 to 90 percent duty cycle range, and the low idle is in the 10 to 22 percent duty cycle range. During normal operation, you may also notice that more movement of the throttle is required for the throttle position status to increase above three percent. You may also observe that the status reaches the 100 percent value prior to the limit of the high idle position. This is done in order to ensure that the throttle reaches these two critical points for engine operation.

Expected Result:

Result 1 Diagnostic code 91-8 is active.

Result 2 Diagnostic code 41-3 is active.

Result 3 There are no active diagnostic codes that are related to the sensor circuit for the position of the digital throttle at this time, but a fault is suspected with operation of the sensor circuit.

Results:

• Result 1 - Proceed to Test Step 3.

• Result 2 - Proceed to Test Step 5.

• Result 3 - Proceed to Test Step 3.

Test Step 3. Check the Duty Cycle of the Digital Throttle Position Sensor

1. Verify that the keyswitch is in the ON position.

2. Monitor the duty cycle of the throttle sensor on the display screen of the electronic service tool.

Expected Result:

The duty cycle is between 10 and 22 percent with the throttle assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the throttle assembly in the high idle position.

Results:

• OK - The digital throttle position sensor is operating correctly. Proceed to Test Step 6.

• Not OK - The digital throttle position sensor circuit is not operating correctly. Proceed to Test Step 4.

Test Step 4. Check the Supply Voltage at the Digital Throttle Position Sensor

1. Turn the keyswitch to the OFF position.

2. Install a breakout "T" with 3 terminals at the digital throttle position sensor connector J403/P403.

3. Turn the keyswitch to the ON position.

4. Measure the voltage at terminal "A" (+8 Volts) with reference to terminal "B" (digital throttle position sensor ground).

Expected Result:

The measured voltage is between 7.5 Volts DC and 8.5 Volts DC for the digital throttle position sensor.

Results:

• OK - Proceed to Test Step 8.

• Not OK - The sensor is not receiving the correct voltage. Proceed to Test Step 5.

Test Step 5. Monitor the Electronic Service Tool while the Digital Throttle Position Sensor is Being Disconnected

1. Access the active diagnostic code screen on the electronic service tool. Ensure that one of the following diagnostic code is active before proceeding:
   • 41-3

   • 41-4

2. Monitor the active diagnostic code screen while the digital throttle position sensor is being disconnected and reconnected.

Expected Result:

One of the following diagnostic codes is still active after the digital throttle position sensor has been disconnected:

• 41-3

• 41-4

Results:

• OK - Ensure that the digital throttle position sensor has been reconnected before continuing. Proceed to Test Step 7.

• Not OK -

  Repair: Perform the following diagnostic procedure:Temporarily install another digital throttle position sensor. Use the electronic service tool in order to check for an active +8 Volt DC diagnostic code. Replace the digital throttle position sensor if both of the following conditions occur:

  • The fault is corrected with the new digital throttle position sensor.

  • The fault returns after the old digital throttle position sensor has been reconnected.

  STOP

Test Step 6. Check the Status of the PTO On/Off Switch and the Status of the Power Train Data Link with the Electronic Service Tool

1. Check the status of the "PTO ON/OFF Switch" with the electronic service tool in order to verify that the "PTO ON/OFF Switch" is switched OFF. The PTO mode may cause the ECM to ignore the digital throttle position sensor if demand is less than the PTO speed demand.

2. Start the engine. Use the electronic service tool in order to monitor the throttle position status. While the throttle position status is being monitored, operate the throttle over the full range of movement. The throttle position status and the engine should respond to the change in the throttle position.

3. Go to the "Configuration Settings" screen on the electronic service tool and turn off the "Torque Speed Control".

   Note: The "Torque Speed Control" is an option that may be installed by the OEM.

4. While the throttle position status is being monitored, operate the throttle over the full range of movement. Also, monitor the response of the engine when the throttle is operated.

Expected Result:

The throttle position status and the engine should respond to the change in the throttle position.

Result 1 The digital throttle position sensor functions correctly.

Result 2 The throttle response is limited by a "Torque Speed Control" message.

Result 3 The PTO limits the throttle response.

Results:

• Result 1 - The digital throttle position sensor is operating correctly. Continue troubleshooting until the original condition is resolved.STOP

• Result 2 - The engine response is normal when the "Torque Speed Control Link" setting is disabled. However, the engine does not respond when the "Power Train Data Link" is enabled. A component within the "Power Train Data Link" setting is causing the response fault. Refer to the OEM documentation in order to repair the faulty component in the "Power Train Data Link". STOP

• Result 3 - The ECM is operating in PTO mode.

  Repair: If the PTO should not be active, refer to the following diagnostic procedure: Troubleshooting, "PTO Switch Circuit - Test"

  STOP

Test Step 7. Disconnect the Power Supply Connections for the Digital Throttle Position Sensor at the ECM

1. Turn the keyswitch to the OFF position.

2. Disconnect connector P1. Remove the P1:43 (+8 Volts). Remove the P1:33 (digital throttle position sensor ground) from connector P1.

3. Reconnect the P1 connector to the ECM.

4. Turn the keyswitch to the ON position.

5. Use the electronic service tool to check for active diagnostic codes.

Expected Result:

One of the following diagnostic codes is still active after the terminals for sensor power have been disconnected:

• 41-3

• 41-4

Results:

• OK -

  Repair: Perform the following repair: Check the battery voltage at pins 1, 2, 3, 9 and 10 (Battery ground) on the P1 connector. Check the battery voltage at pins 7, 8, 15, and 16 (Battery+) on the J1 connector.. The measured voltage should be in one of the following ranges:

  • For 12 Volt systems, the voltage should be between 11.0 Volts DC and 13.5 Volts DC.

  • For 24 Volt systems, the voltage should be between 22.0 Volts DC and 27.0 Volts DC.

  If the voltage is correct, then perform the following procedure.

  1. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

  2. Contact the Technical Communicator.

     Note: This consultation can greatly reduce the repair time.

  3. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

  4. Use the electronic service tool to recheck the system for active diagnostic codes.

  5. If the fault is resolved with the test ECM, reconnect the suspect ECM.

  6. If the fault returns with the suspect ECM, replace the ECM.

  7. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

• Not OK -

  Repair: Perform the following repair:There is a fault in the harness between the ECM and the digital throttle position sensor. While active diagnostic codes are being monitored, connect the removed wires one at a time in order to verify that the active diagnostic codes reappear. Replace pin P1:33 (digital throttle position sensor ground). Replace pin P1:43 (+8 Volts). This procedure is used to find the wire that is causing the fault. Repair the harness or replace the harness, as required.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

Test Step 8. Check the Duty Cycle of the Throttle Position Sensor at the Sensor

Note: Performing certain steps within this procedure requires the use of a multimeter that is capable of measuring a PWM duty cycle.

1. Turn the keyswitch to the OFF position.

2. Remove the signal wire for the digital throttle position sensor (terminal "C") from P403. Refer to illustration 1.

3. Install a breakout "T" with three terminals at the digital throttle position sensor connector J403/P403.

4. Connect the multimeter probes to terminal "C" (digital throttle position sensor signal) and terminal "B" (digital throttle position sensor ground) of the breakout T.

5. Turn the keyswitch to the ON position.

6. While the duty cycle is being monitored on the multimeter, operate the throttle through the full range of movement.

Expected Result:

The duty cycle is between 10 and 22 percent with the throttle assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the throttle assembly in the high idle position.

Results:

• OK - Reinsert the wire (terminal "C") into the harness connector of the digital throttle position sensor. The digital throttle position sensor is working correctly. Proceed to Test Step 9.

• Not OK - Leave the multimeter probe connected to the breakout "T". Insert the wire (terminal "C") into the machine harness connector. The throttle pedal assembly is faulty. Proceed to Test Step 10.

Test Step 9. Check the Duty Cycle of the Accelerator Pedal Position Sensor at the ECM

Note: Performing certain steps within this procedure requires the use of a multimeter that is capable of measuring a PWM duty cycle.

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector and then remove pin P1:53 (digital throttle position sensor signal).

3. Connect the multimeter probes between the removed wire and pin P1:33 (digital throttle position sensor ground).

4. Reconnect the P1 connector to the ECM.

5. Turn the keyswitch to the ON position.

6. Use the multimeter in order to display the duty cycle output of the digital throttle position sensor. While the duty cycle output of the digital throttle position sensor is being monitored on the multimeter, move the throttle assembly from the low idle position to the high idle position. Record the results.

7. Turn the keyswitch to the OFF position.

8. Remove the P1 connector from the ECM.

9. Install pin P1:53.

10. Connect the P1 connector to the ECM.

Expected Result:

The duty cycle is between approximately 10 and 22 percent with the throttle assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the throttle assembly in the high idle position.

Results:

• OK - A good signal from the digital throttle position sensor is reaching the ECM.

  Repair: Check for the correct supply voltage at the ECM. If the voltage is correct, then perform the following procedure.

  1. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

  2. Contact the Technical Communicator.

     Note: This consultation can greatly reduce the repair time.

  3. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

  4. Use the electronic service tool to recheck the system for active diagnostic codes.

  5. If the fault is eliminated with the test ECM, reconnect the suspect ECM.

  6. If the fault returns with the suspect ECM, replace the ECM.

  7. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

• Not OK - There is a fault with signal wire in the harness. Proceed to Test Step 11.

Test Step 10. Remove the Digital Throttle Position Sensor from the Throttle Pedal Assembly

Illustration 3	g01185326
Typical throttle assembly (1) Sensor mounting face (2) Sensor drive key (3) Mounting screw holes

Illustration 4	g01185327
Throttle block assembly (1) Mounting screw holes (2) Sensor housing (3) Sensor drive slot

Illustration 5	g01185328
Throttle block assembly (1) Mounting screw holes (2) Sensor drive slot (3) Sensor mounting face

1. Verify that the keyswitch is in the OFF position.

2. Note the sensor orientation in the throttle assembly and the sensor connector for the harness routing prior to sensor removal. Remove the digital throttle position sensor from the throttle assembly. Thoroughly inspect the connector and the harness for signs of abrasion.

3. Connect a multimeter that is capable of measuring a PWM duty cycle to terminal "C" of the breakout "T".

4. Turn the keyswitch to the ON position.

5. Display the duty cycle output of the digital throttle position sensor while the sensor slot is released. Use a screwdriver to advance the sensor slot to the maximum position. Refer to Illustration 5.

Expected Result:

When the sensor is removed from the throttle assembly and the sensor slot is released, the duty cycle is 10 percent or less. When the sensor slot is moved to the maximum position, the duty cycle increases to 90 percent or more.

Results:

• OK - The digital throttle position sensor is working correctly. Refer to the OEM dealer for correct replacement of the throttle assembly. STOP

• Not OK - The digital throttle position sensor is faulty. Check the throttle assembly in order to ensure that the throttle assembly is not causing damage to the sensor. If the throttle assembly is causing damage to the sensor, refer to the OEM dealer for correct replacement of the throttle assembly. If the throttle assembly appears OK, replace the digital throttle position sensor.STOP

Test Step 11. Route the Supply Bypass Wires to the Digital Throttle Position Sensor

1. Turn the keyswitch to the OFF position.

2. Temporarily remove the signal wire for the digital throttle position sensor from P1:53.

3. Remove terminal "C" (digital throttle position sensor signal) from the digital throttle position sensor connector.

4. Route the new wiring from the ECM to the digital throttle position sensor.

5. Turn the keyswitch to the ON position.

6. Check the duty cycle of the digital throttle position sensor on the electronic service tool while the digital throttle assembly is being moved over the full range.

Expected Result:

The duty cycle is between 10 and 22 percent with the throttle assembly in the low idle position, and the duty cycle is between 75 and 90 percent with the throttle assembly in the high idle position.

Results:

• OK -

  Repair: Perform the following repair:The wiring from the ECM to the digital throttle position sensor appears faulty. Permanently install new wiring.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

• Not OK - Double check the wiring, the P1/J1 connectors and the digital throttle position sensor connector. If a fault still exists, repeat the test procedure from Test Step 1.STOP