The throttle position sensor is mounted to a pedal assembly. The throttle position sensor provides a signal to the ECM. The geometry of the pedal assembly controls both the travel of the sensor and the range of the output signal. The throttle position sensor cannot be adjusted.
The output of the throttle position sensor is a pulse width modulated signal that varies with the position of the throttle. The throttle position sensor produces a minimum duty cycle in the released position. The throttle position sensor produces a maximum duty cycle in the fully depressed position. When the pedal is released, the ECM translates the output signal to a throttle position of 0%. When the pedal is fully depressed, the ECM translates the output signal to a throttle position of 100%.
Note: The throttle position sensor receives a supply of 8 VDC from the ECM. This supply is common with all digital sensors. Troubleshoot any active diagnostic codes that are related to the digital sensor supply before attempting this troubleshooting procedure.
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| Illustration 1 | g00733592 |
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Schematic | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the keyswitch to the OFF/RESET position.
- Thoroughly inspect the J1/P1 ECM connector, the J3/P3 machine connector, and the J35/P35 throttle position sensor connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Expected Result:
All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points.
Results:
- OK - Proceed to Test Step 2.
- Not OK -
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP
Test Step 2. Inspect the Throttle Pedal Assembly
- Inspect the throttle pedal assembly for components that are loose, bent, missing, or worn.
- Slowly depress the pedal and release the pedal.
Expected Result:
The throttle pedal assembly should operate smoothly without excessive drag. The pedal should return to the low idle position without assistance in less than one second.
Results:
- OK - The throttle pedal assembly functions properly. Proceed to Test Step 3.
- Not OK -
Repair: Repair the throttle pedal assembly, as required.
STOP
Test Step 3. Check the Status on the Electronic Service Tool
- Connect the electronic service tool to the service tool connector.
- Turn the keyswitch to the ON position.
- Observe the status for "Throttle Position" on the electronic service tool while you operate the throttle pedal.
Expected Result:
The status should be approximately 0 percent when the throttle pedal is released. The status should progressively increase to 100 percent when the throttle pedal is fully depressed.
Note: This range can change depending on the adjustment of the throttle pedal assembly.
Results:
- OK - The throttle position sensor is working properly.
Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.
STOP
- Not OK - Proceed to Test Step 4.
Test Step 4. Check the Supply Voltage at the Sensor
- Install a 7X-6370 Adapter Cable (3 Pin DT Breakout) at the J35/P35 throttle position sensor connector.
- Turn the keyswitch to the ON position.
- Measure the voltage across terminal A (Digital Sensor +8 VDC) and terminal B (Digital Return) at the J35/P35 breakout.
Expected Result:
The supply voltage should be 8.0 ± 0.5 VDC.
Results:
- OK - The sensor is receiving the correct supply voltage. Proceed to Test Step 5.
- Not OK - Proceed to Test Step 10.
Test Step 5. Check the Isolated Signal Frequency and the Duty Cycle at the Sensor
- Remove the wire from the harness side of P35:C (Signal).
- Turn the keyswitch to the ON position.
- Measure the frequency and the duty cycle between terminal B (Digital Return) and terminal C (Signal) at the J35/P35 breakout while you operate the throttle pedal.
- Turn the keyswitch to the OFF/RESET position.
- Reinstall the wire in P35:C (Signal).
Expected Result:
The frequency should be between 150 and 1000 Hz. The duty cycle should be between 10 and 22 percent when the pedal is released. The duty cycle should be between 75 and 90 percent when the pedal is fully depressed.
Results:
- OK - The sensor is producing a valid signal. Proceed to Test Step 6.
- Not OK - The sensor is not producing a valid signal.
Repair: Replace the throttle position sensor.
Verify that the repair eliminates the problem.
STOP
Test Step 6. Check for a Short Circuit in the Wiring Harness
- Disconnect the J1/P1 ECM connector, the J2/P2 ECM connector, and the J35/P35 throttle position sensor connector.
- Measure the following resistances:
- P35:A (Digital Sensor +8 VDC) to P35:B (Digital Return)
- P35:A (Digital Sensor +8 VDC) to P35:C (Throttle Position)
- P35:B (Digital Return) to P35:C (Throttle Position)
Expected Result:
The resistance should be greater than 20,000 Ohms for each measurement.
Results:
- OK - There are no shorts in the harness. Proceed to Test Step 7.
- Not OK - There is a short circuit in the harness or connectors.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP
Test Step 7. Check the Resistance through the Harness
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| Illustration 2 | g00746300 |
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P1 ECM connector | |
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| Illustration 3 | g00934902 |
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P2 ECM connector | |
- Fabricate a jumper wire with pins at both ends.
- Use the jumper wire to short P35:A (Digital Sensor +8 VDC) and P35:C (Throttle Position) together.
- Measure the resistance between P2:31 (Throttle Position) and P1:35 (Digital Sensor +8 VDC).
- Move the one end of the jumper wire from P35:A (Digital Sensor +8 VDC) to P35:B (Digital Return). Leave the other end in P35:C (Throttle Position).
- Measure the resistance between P2:31 (Throttle Position) and P1:29 (Digital Return).
- Remove the jumper wire and reconnect all of the connectors.
Expected Result:
The resistance should be less than 10 Ohms for each measurement.
Results:
- OK - The harness is good. Proceed to Test Step 8.
- Not OK - There is an open circuit or excessive resistance in the harness or the connectors.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP
Test Step 8. Check the Signal Frequency and the Duty Cycle at the ECM
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| Illustration 4 | g00746300 |
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J1/P1 breakout | |
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| Illustration 5 | g00934902 |
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J2/P2 breakout | |
- Install a 7X-1715 Adapter Cable (40 Pin Breakout T) at the J1/P1 ECM connector.
- Install a 7X-1715 Adapter Cable (40 Pin Breakout T) at the J2/P2 ECM connector.
- Turn the keyswitch to the ON position.
- Measure the frequency and measure the duty cycle between P2:31 (Throttle Position) and P1:29 (Digital Return) at the breakouts while you operate the throttle pedal.
- Turn the keyswitch to the OFF/RESET position.
Expected Result:
The frequency should be between 150 and 1000 Hz. The duty cycle should be between 10 and 22 percent when the pedal is released. The duty cycle should be between 75 and 90 percent when the pedal is fully depressed.
Results:
- OK - A valid sensor signal is reaching the ECM. Proceed to Test Step 9.
- Not OK - There is an intermittent problem in the wiring harness or the connectors.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP
Test Step 9. Check the Status on the Electronic Service Tool
- Turn the keyswitch to the ON position.
- Observe the status for "Throttle Position" on the electronic service tool while you operate the throttle pedal.
Expected Result:
The status should read approximately 0 percent when the throttle pedal is released. The status should progressively increase to 100 percent when the throttle pedal is fully depressed.
Note: This range can change depending on the adjustment of the throttle pedal assembly.
Results:
- OK - The throttle position sensor is working properly.
Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.
STOP
- Not OK - A valid signal appears at the ECM, but the ECM is not reading the signal properly.
Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.
STOP
Test Step 10. Check the Supply Voltage at the ECM
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| Illustration 6 | g00746300 |
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J1/P1 breakout | |
- Install a 7X-1715 Adapter Cable (40 Pin Breakout T) at the J1/P1 ECM connector.
- Turn the keyswitch to the ON position.
- Measure the voltage between P1:29 (Digital Return) and P1:35 (Digital Sensor +8 VDC) at the J1/P1 breakout.
- Turn the keyswitch to the OFF/RESET position.
Expected Result:
The supply voltage should be 8.0 ± 0.5 VDC.
Results:
- OK - There is an open circuit or excessive resistance in the harness between the ECM and the sensor.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP
- Not OK - The ECM does not appear to be producing the correct supply voltage.
Repair: Troubleshoot the digital sensor supply. Refer to Troubleshooting, "Digital Sensor Supply Circuit - Test" for the correct procedure.
STOP