C13 and C15 On-highway Engines Caterpillar

Table 1 lists the diagnostic codes that are covered by this procedure.

Background Information for the Accelerator Pedal Position Sensor

The accelerator pedal position sensor provides a throttle position signal to the Engine Control Module (ECM). The sensor is attached directly to the accelerator pedal assembly. The sensor cannot be adjusted.

The accelerator pedal position sensor is powered by the 8 volt supply inside the ECM. The sensor's output is a constant frequency signal with a duty cycle that varies with the pedal position. The sensor produces a minimum duty cycle of 10 percent at low idle and a maximum of 90 percent when the accelerator pedal is fully depressed. The ECM translates the duty cycle into an accelerator pedal position of 3 to 100 percent. Caterpillar Electronic Technician (ET) displays the value of the accelerator pedal position as "Accelerator Pedal Position".

Automatic Calibration

The ECM performs a new calibration of the accelerator pedal position sensor whenever the ECM is powered up.

Initially, the ECM assumes that 22 percent duty cycle is equal to three percent of "Accelerator Pedal Position". As a result, some movement of the accelerator pedal may be required for the "Accelerator Pedal Position" to increase above three percent. The ECM assumes that 75 percent duty cycle is equal to 100 percent of "Accelerator Pedal Position". As a result, the "Accelerator Pedal Position" may reach 100 percent well before the accelerator pedal is fully depressed. This is normal operation.

After some cycling of the accelerator pedal from the low idle position to the high idle position, the ECM automatically adjusts the "Accelerator Pedal Position" so that the entire available output from the sensor is used.

Accelerator Pedal Position Sensor and PTO Operation

If the vehicle uses the ECM dedicated PTO functions, the output from the accelerator pedal position sensor is affected by several parameters. The "PTO Configuration" can be programmed to one of these three values:

Remote Switches - The output from the accelerator pedal position sensor is ignored.

Remote Throttle - The output from the accelerator pedal position sensor is ignored.

Cab Switches - The output from the accelerator pedal position is ignored if the "PTO Cab Throttle RPM Limit" is programmed to "Low Idle".

Illustration 1	g00642016
Typical schematic for the cab's accelerator pedal position sensor

Note: The return wire may be connected to P1-3, P1-5, or P1-18.

Background Information for the Remote Accelerator Position Sensor

A remote accelerator position sensor may be used for PTO purposes. The remote accelerator position sensor must be connected to terminal J1/P1-68 of the Engine Control Module (ECM). Before the ECM will respond to the remote accelerator position sensor, the ECM "PTO Configuration" must be programmed to "Remote Throttle", and the "PTO On/Off Switch" must be in the ON position.

The remote accelerator position sensor must be powered from the vehicle battery (+12 VDC or +24 VDC). A version of the accelerator position sensor that is powered by the vehicle's battery must be used for the remote accelerator position sensor, and a accelerator pedal position sensor that is powered by +8 VDC from the ECM must be used in the cab.

The ECM will not respond to the remote accelerator position sensor while a 630-2 (J1939) Calibration Memory : Erratic, Intermittent, or Incorrect code is active. Refer to Troubleshooting, "ECM Memory - Test" if the 630-2 (J1939) diagnostic code is active.

The remote accelerator position sensor provides a throttle position signal to the ECM. The output of the remote accelerator position sensor is a constant frequency signal with a pulse width that varies with the position of the sensor. This output signal is referred to as either a duty cycle or a pulse width modulated signal (PWM).

The output signal of the remote accelerator position sensor is expressed as a percentage between 3 and 100 percent. The accelerator position sensor will produce a duty cycle of 10 to 22 percent at low idle and 75 to 90 percent when the sensor is fully actuated. The percent of duty cycle is translated in the ECM into a throttle position of 3 to 100 percent.

If the vehicle is using the ECM dedicated PTO functions, the accelerator position sensor will be ignored while the engine is in "PTO Mode" and the "PTO Configuration" is programmed to the "Remote Throttle" option.

The ECM is in "PTO Mode" while the PTO on/off switch is ON. This can be checked through the status screen on Caterpillar Electronic Technician (ET).

The ECM will not respond to the remote accelerator position sensor when both of the following conditions are met:

• The PTO on/off circuit is switched from the OFF position to the ON position.

• The ECM reads the remote accelerator position sensor above low idle.

This prevents the engine from experiencing unexpected acceleration or sudden acceleration when the PTO on/off circuit is turned ON. The remote accelerator position sensor must return to low idle before the ECM will respond. The ECM must also see a transition from the OFF position to the ON position in the PTO on/off switch in order to allow the other PTO speed control functions to operate. If the engine is started with the PTO on/off switch in the ON position, the accelerator will respond. The response will occur only if the accelerator pedal is first returned to the low idle position. The other engine speed controls will not respond.

Illustration 2	g01275106
Typical schematic for remote accelerator pedal position sensor

Note: The return wire may be connected to P1-3, P1-5, or P1-18.

Illustration 3	g01182700
P1 terminals for the pulse width modulated sensors (PWM) (3) Return (4) + 8V (5) Return (18) Return (66) Accelerator pedal position (68) Remote accelerator position sensor

Test Step 1. Inspect Electrical Connectors and Wiring

1. Thoroughly inspect ECM vehicle harness connector J1/P1, the firewall bulkhead connector and the accelerator pedal 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 accelerator pedal position sensor.

3. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

4. Check the harness and wiring for abrasion and for pinch points from the accelerator pedal position sensor to the ECM.

Expected Result:

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

Results:

• Yes - The wiring is OK. Proceed to Test Step 2.

• No - The wiring is not OK.

  Repair: Perform the following repair:

  Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.

  Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect Cat ET to the data link connector.

2. Turn the keyswitch to the ON position.

3. Monitor the active diagnostic code screen on Cat ET. Check and record active diagnostic codes.

Expected Result:

There is an active diagnostic code for the accelerator pedal position sensor or for the 8 volt supply.

Results:

• "8 volt suppy" active code - There is an active diagnostic code for the 8 volt supply. Proceed to Test Step 5.

• "Accelerator pedal" active code - There is an active diagnostic code for the accelerator pedal position sensor. Proceed to Test Step 3.

• "Remote accelerator" active code - There is an active diagnostic code for the remote accelerator position sensor. Proceed to Test Step 12.

• No active code - Proceed to Test Step 3.

Test Step 3. Check the Duty Cycle of the Accelerator Pedal Position Sensor

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

2. Monitor the duty cycle of the throttle sensor on Cat ET. Access the following display screens in order:

   • "Service"

   • "Calibrations"

   • "Monitor Throttle Position Sensor"

Expected Result:

The duty cycle is between 10 and 22 percent with the accelerator pedal assembly in the Low Idle position, and the duty cycle is between 75 and 90 percent with the accelerator pedal assembly in the High Idle position.

Results:

• OK - The accelerator pedal position sensor is operating correctly. Proceed to Test Step 6.

• Not OK - The accelerator pedal position sensor is not operating correctly. Proceed to Test Step 4.

Test Step 4. Check the Supply Voltage at the Accelerator Pedal Position Sensor

1. Turn the keyswitch to the OFF/RESET position.

2. Install a breakout T with three terminals at the accelerator pedal position sensor connector J403/P403.

3. Turn the keyswitch to the ON position.

4. Measure the voltage at terminal "A" (+8 V) with reference to terminal "B" (accelerator/switch sensor common).

Expected Result:

The measured voltage is between 7.5 VDC and 8.5 VDC for the pedal mounted throttle position sensor that is used in the cab.

Results:

• OK - The voltage reading is correct. Proceed to Test Step 8.

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

Test Step 5. Monitor Cat ET while the Accelerator Pedal Position Sensor is Disconnected

Monitor the active diagnostic code screen while the accelerator pedal position sensor is disconnected.

Expected Result:

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

• 8 Volt Supply voltage high

• 8 Volt Supply voltage low

Results:

• Yes - There is an active diagnostic code for the 8 volt supply after the sensor is disconnected. Connect the accelerator pedal position sensor. Proceed to Test Step 7.

• No - There is no active code for the 8 volt supply after the sensor is disconnected.

  Repair: Perform the following diagnostic procedure:

  Temporarily install another accelerator pedal position sensor. Check for an active +8 V diagnostic code. Replace the accelerator pedal position sensor if both of the following conditions occur:

  • The problem is corrected with the new accelerator pedal position sensor.

  • The problem returns after the old accelerator pedal 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 Cat ET

1. Check the status of the "PTO ON/OFF Switch" on Cat ET in order to verify that the "PTO ON/OFF Switch" is off. The PTO mode may cause the ECM to ignore the accelerator pedal position sensor if the "PTO Configuration" is programmed to one of the following parameters:

   • Remote switches

   • Remote throttle

   • Cab switches

   Note: If the "PTO Configuration" is programmed to "Cab Switches" and the "PTO Cab Controls RPM Limit" is programmed to "Low Idle", the PTO mode may cause the ECM to ignore the accelerator pedal position sensor. This will occur when the "PTO ON/OFF Switch" is in the ON position.

2. Start the engine. While the "Throttle Position" status is being monitored on Cat ET, depress the accelerator pedal and release the accelerator pedal. The "Throttle Position" status and the engine should respond to the change in the accelerator pedal position.

3. Go to the "System Troubleshooting Settings" portion of Cat ET and turn off the "Power Train Data Link".

4. While the "Throttle Position" status is being monitored, depress the accelerator pedal and release the accelerator pedal. Also depress the accelerator pedal and release the accelerator pedal while the engine response is being monitored.

Expected Result:

The "Throttle Position" status and the engine respond to the change in the accelerator pedal position.

Result 1 The cab accelerator functions properly.

Result 2 The throttle response is limited by a message from a device on the power train data link.

Result 3 The PTO limits the throttle response.

Results:

• Result 1 - The accelerator pedal position sensor is operating correctly. Continue troubleshooting until the original condition is resolved.

  STOP

• Result 2 - If the engine responds with the "Power Train Data Link" in a disabled condition and the engine does not respond with the "Power Train Data Link" in an enabled condition, a component of the "Power Train Data Link" is causing the response problem of the accelerator pedal position sensor. Send the truck to the vehicle manufacturer in order to repair the faulty component of 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, "Power Take-Off - Test"

  STOP

Test Step 7. Disconnect the Power Supply Connections for the Accelerator Pedal Position Sensor at the ECM

1. Turn the keyswitch to the OFF/RESET position.

2. Remove terminal 4 (+8 VDC) and the terminal for the return from the vehicle harness connector P1.

3. Turn the keyswitch to the ON position.

4. Use Cat ET to check for active diagnostic codes.

Expected Result:

The active code for the 8 volt supply is gone when the terminals are removed from the P1 connector.

Results:

• Yes - The active code for the 8 volt supply is gone when the terminals are removed from the P1 connector.

  Repair: There is a problem in the wiring between the ECM and the accelerator pedal 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. First connect P1-5 and then connect the terminal for the return. This procedure is used to find the wire that is causing the problem. Repair the wire or replace the wire, as required. Verify that the repair eliminates the problem.

  STOP

• Not OK -

  Repair: Perform the following repair:

  Temporarily connect a test ECM. Use Cat ET to verify that the active diagnostic code is resolved. If the problem is corrected with the test ECM, reconnect the suspect ECM. Verify that the active diagnostic code returns. If the active diagnostic code returns with the suspect ECM, replace the ECM.

  STOP

Test Step 8. Check the Duty Cycle of the Accelerator Pedal 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/RESET position.

2. Remove the signal wire for the accelerator pedal position sensor (terminal "C") from P403. This is the vehicle harness side of the accelerator pedal position sensor connector.

3. Install a breakout T with three terminals at the accelerator pedal position sensor connector J403/P403.

4. Connect the multimeter probes to terminal "C" (accelerator pedal position) and terminal "B" (accelerator/switch sensor common) of the breakout T.

5. Turn the keyswitch to the ON position.

6. While the duty cycle is being monitored on the multimeter, depress the accelerator pedal and release the accelerator pedal.

Expected Result:

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

Results:

• OK - Insert the wire (terminal "C") into the vehicle harness connector. The accelerator pedal position sensor is working correctly. Proceed to Test Step 9.

• Not OK - Leave the PWM probe connected to the breakout T. Insert the wire (terminal "C") into the vehicle harness connector. The accelerator pedal position sensor or the accelerator 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/RESET position.

2. Remove the wire for the accelerator pedal position sensor P1-66. You may be required to disconnect ECM connector P1 in order to remove the terminal for the signal input of the accelerator pedal position sensor.

3. Connect the multimeter probes between the removed wire and P1-5 (accelerator/switch sensor common).

4. Reconnect ECM connector P1 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 accelerator pedal position sensor. While the duty cycle output of the accelerator pedal position sensor is being monitored on the multimeter, move the accelerator pedal from the low idle position to the high idle position. Record the results.

7. Turn the keyswitch to the OFF/RESET position.

8. Insert P1-66 into the ECM vehicle connector P1.

Expected Result:

The duty cycle is between 10 and 22 percent with the accelerator pedal in the Low Idle position, and the duty cycle is between 75 and 90 percent with the accelerator pedal in the High Idle position.

Results:

• OK - A good signal from the accelerator pedal position sensor is reaching the ECM. Verify that the ECM is receiving the proper battery voltage. If the ECM is receiving the proper battery voltage, temporarily connect a test ECM and verify that the problem is resolved. If the problem disappears with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM.

  STOP

• Not OK - There is a problem with signal wire for the accelerator pedal position sensor in the vehicle wiring harness. Proceed to Test Step 11.

Test Step 10. Remove the Accelerator Pedal Position Sensor from the Accelerator Pedal Assembly

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

2. Remove the accelerator pedal position sensor from the accelerator pedal assembly. Note the sensor's orientation in the accelerator pedal assembly, and the sensor's harness routing prior to sensor removal. Thoroughly inspect the harness connector for signs of abrasion.

3. Connect the 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 accelerator pedal position sensor while the sensor slot is released. Use a screwdriver to advance the sensor slot to the maximum position. Refer to Illustration 4.

   When the sensor is removed from the accelerator pedal assembly, a 91-13 (J1939) diagnostic code may be activated. This is normal. The diagnostic code should disappear when the sensor is assembled back into the accelerator pedal assembly.

Illustration 4	g00706977
Accelerator pedal assembly

Expected Result:

When the sensor is removed from the accelerator pedal 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 accelerator pedal position sensor is working correctly. Clear any diagnostic codes that were caused by performing this test procedure. Refer to the OEM dealer for correct replacement of the accelerator pedal assembly.

  STOP

• Not OK - The accelerator pedal position sensor is faulty.

  Repair: Check the accelerator pedal assembly in order to ensure that the accelerator pedal assembly is not causing damage to the sensor. If the accelerator pedal assembly is causing damage to the sensor, refer to the OEM dealer for correct replacement of the accelerator pedal assembly. If the accelerator pedal assembly appears OK, replace the accelerator pedal position sensor.

  STOP

Test Step 11. Route the Supply Bypass Wires to the Accelerator Pedal Position Sensor

1. Turn the keyswitch to the OFF/RESET position.

2. Remove the signal wire for the accelerator pedal position sensor from the ECM connector P1-66.

3. Remove terminal "C" (accelerator pedal position) from the accelerator pedal position sensor connector.

4. Route new wiring from the ECM to the accelerator pedal position sensor.

5. Turn the keyswitch to the ON position.

6. Check the duty cycle of the accelerator pedal position sensor on Cat ET while the accelerator pedal is being moved over the full range.

Expected Result:

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

Results:

• OK - The indications are correct.

  Repair: Perform the following repair:

  The wiring from the ECM to the accelerator pedal position sensor appears faulty. Permanently install new wiring.

  Verify that the repair eliminates the problem.

  STOP

• Not OK - The indications are not correct.

  Repair: Repair the wiring, the ECM vehicle harness connector J1/P1 and/or the sensor connector. Verify that the problem is resolved.

  STOP

Test Step 12. Check the Supply Voltage for the Remote Accelerator Position Sensor

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

2. Measure the voltage between terminal "A" (+12 V) and terminal "B" (sensor common) at J406 remote accelerator position sensorconnector.

Expected Result:

The measured voltage is between 11.0 VDC and 13.5 VDC.

Results:

• Yes - The voltage is OK. Proceed to Test Step 13.

• No - The voltage is not OK. The vehicle wiring or the battery is causing the problem.

  Repair: Repair the wiring or the battery. Replace the wiring or the battery. Perform the repair that is necessary. Verify that the problem is resolved.

  STOP

Test Step 13. Check the Duty Cycle of the Remote Accelerator Pedal Position Sensor

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

2. Monitor the duty cycle of the PTO throttle sensor on Cat ET. Access the following display screen in order:

   • "Service"

   • "Calibrations"

   • "Monitor Throttle Position Sensor"

3. Operate the throttle position sensor throughout the entire range.

Expected Result:

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

Results:

• OK - The remote accelerator position sensor is operating correctly. Proceed to Test Step 14.

• Not OK - The remote accelerator position sensor is not operating correctly. Proceed to Test Step 15.

Test Step 14. Check the Status of the Power Train Data Link on Cat ET

1. Start the engine. While the status of the "PTO Throttle Position" is being monitored on Cat ET, actuate the remote throttle. The throttle position status and the engine should respond to the change in the throttle position.

2. Go to the "System Troubleshooting Settings" section of Cat ET and turn off the power train data link.

3. While the status of the "PTO Throttle Position" is being monitored on Cat ET, actuate the remote throttle. Also, actuate the remote throttle while the engine response is being monitored.

Expected Result:

The status of the "PTO Throttle Position" and the engine responds to the change in the position of the remote throttle position sensor.

Result 1 The remote throttle position sensor is functioning properly.

Result 2 The throttle response is limited by a message from the power train data link.

Results:

• Result 1 - The remote accelerator position sensor is operating correctly. Continue troubleshooting until the original condition is resolved.

  STOP

• Result 2 - The remote accelerator position sensor is not operating correctly.

  Repair: If the engine responds with the power train data link in the OFF position, but not with the power train data link in the ON position, a component of the power train data link is causing the response problem of the remote accelerator position sensor. Send the vehicle to the vehicle manufacturer in order to repair the faulty component of the power train data link.

  STOP

Test Step 15. Check the Duty Cycle of the Remote Accelerator Position Sensor at the Sensor

1. Turn the keyswitch to the OFF position.

2. Remove terminal J406-C (throttle position signal) from the connector for the remote accelerator position sensor. This is the vehicle harness side of the connector.

3. Install a breakout T at connector J406/P406.

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

5. Turn the keyswitch to the ON position.

6. While the duty cycle is being monitored on the multimeter, actuate the remote accelerator position sensor.

Expected Result:

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

Results:

• OK - The readings are correct. Return the J406/P406 connectors to the original configuration. The sensor is working correctly. Proceed to Test Step 16.

• Not OK - The readings are not correct. Leave the PWM probe connected to the breakout T. Insert wire C into the J406 connector. The sensor or the accelerator control is faulty. Proceed to Test Step 17.

Test Step 16. Check the Duty Cycle of the Remote Accelerator Position Sensor at the ECM

1. Turn the keyswitch to the OFF position.

2. Remove terminal P1-68 (sensor signal) from the ECM connector.

3. Connect the multimeter's probes between the wire for the remote accelerator position sensor and the sensor common.

4. Turn the keyswitch to the ON position.

5. Use the multimeter in order to display the duty cycle output of the remote accelerator position sensor. While the duty cycle output of the remote accelerator position sensor is being monitored on the multimeter, actuate the remote throttle from the low idle position to the high idle position. Record the results.

6. Turn the keyswitch to the OFF position.

Expected Result:

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

Results:

• OK - A good signal from the remote accelerator position sensor is reaching the ECM. Verify that the ECM is receiving the proper battery voltage. If the ECM is receiving the proper battery voltage, temporarily connect a test ECM and verify that the problem is resolved. If the problem disappears with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the suspect ECM.

  STOP

• Not OK - There is a problem with signal wire for the remote accelerator position sensor in the vehicle wiring harness. Proceed to Test Step 18.

Test Step 17. Remove the Remote Accelerator Position Sensor from the Throttle Assembly

1. Turn the keyswitch to the OFF position.

2. Remove the remote accelerator position sensor from the throttle assembly. Note the orientation of the sensor in the accelerator pedal assembly, and routing of the sensor harness prior to sensor removal. Thoroughly inspect the sensor's harness for signs of abrasion.

3. Measure the 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 remote accelerator position sensor while the sensor slot is released. Use a screwdriver to advance the sensor slot to the maximum position. Refer to Illustration 5.

   Note: A 644-13 (J1939) Engine External Speed Command Input : Calibration Required code may be generated when the accelerator position sensor is removed from the accelerator pedal assembly. The diagnostic code should become inactive when the sensor is properly assembled back into the accelerator pedal assembly.

Illustration 5	g00642019
(1) Mounting screw holes (2) Sensor slot (3) Sensor housing (4) Mounting surface for sensor (5) Accelerator pedal assembly (6) Accelerator block assembly

Expected Result:

When the sensor is removed from the accelerator pedal 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 readings are correct. The remote accelerator position sensor is working correctly. Clear any diagnostic codes that were caused by performing this test procedure. Refer to the OEM dealer for correct replacement of the accelerator pedal assembly.

  STOP

• Not OK - The readings are not correct. The remote accelerator position sensor is faulty.

  Repair: Check the accelerator pedal assembly in order to ensure that the accelerator pedal assembly is not causing damage to the sensor. If the accelerator pedal assembly is causing damage to the sensor, refer to the OEM dealer for correct replacement of the accelerator pedal assembly.

  STOP

Test Step 18. Route the Supply Bypass Wires to the Remote Accelerator Pedal Position Sensor

1. Turn the keyswitch to the OFF position.

2. Remove P1-66 (remote accelerator position sensor) from the ECM connector.

3. Remove terminal "C" (sensor signal) from the connector for the remote accelerator position sensor.

4. Route new wiring from the ECM to the remote accelerator position sensor.

5. Turn the keyswitch to the ON position.

6. Check the duty cycle of the remote accelerator position sensor with Cat ET while the accelerator pedal assembly is being moved over the full range.

Expected Result:

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

Results:

• OK - The readings are correct. The wiring from the ECM to the accelerator position sensor is faulty.

  Repair: Repair the wiring, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

• Not OK - The readings are not correct.

  Repair: Replace the remote accelerator pedal position sensor. Verify that the problem is resolved.

  STOP