The sensor for the throttle signal provides a signal to the ECM. The geometry of the throttle lever controls both the travel of the sensor and the range of the output signal. The sensor for the throttle signal cannot be adjusted.
The output of the sensor for the throttle signal is a pulse width modulated signal that varies with the position of the throttle. The sensor for the throttle signal produces a minimum duty cycle in the low idle position. The sensor for the throttle signal produces a maximum duty cycle in the high idle position. When the throttle is moved to the low idle position, the ECM translates the output signal to a throttle signal of 0%. When the throttle is moved to the low idle position the ECM translates the output signal to a throttle signal of 100%.
Note: The sensor for the throttle signal receives a supply voltage of 12 ± 1 VDC from the ECM. Troubleshoot any active diagnostic codes that are related to the sensor supply before attempting this troubleshooting procedure.
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| Illustration 1 | g00984614 |
Schematic for the throttle position sensor | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the keyswitch to the OFF/RESET position.
- Thoroughly inspect the J1/P1 ECM connector, the J61/P61 machine connector, and the J403/P403 sensor for the throttle signal 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 Assembly for the Throttle Lever
- Inspect the assembly for the throttle lever for components that are loose, bent, missing, or worn.
- Slowly operate the throttle lever.
Expected Result:
The assembly for the throttle lever should operate smoothly without excessive drag.
Results:
- OK - The throttle lever functions properly. Proceed to Test Step 3.
- Not OK -
Repair: Repair the assembly for the throttle lever, as required.
Stop.
Test Step 3. Check the Status on an Electronic Service Tool
- Connect an electronic service tool to the service tool connector.
- Turn the keyswitch to the ON position.
- Observe the status of "Throttle Signal" on an electronic service tool while you operate the throttle lever.
Expected Result:
The status should be approximately 0 percent when the throttle lever is at thelow idle position. The status should progressively increase to 100 percent when the throttle lever is moved to the high idle position.
Note: This range can change depending on the adjustment of the assembly for the throttle lever.
Results:
- OK - The sensor for the throttle signal 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 J403/P403 sensor for the throttle signal connector.
- Turn the keyswitch to the ON position.
- Measure the voltage across terminal A (+ Batt) and terminal B (Digital Sensor Return) at the breakout.
Expected Result:
The supply voltage should be 12 ± 1 VDC.
Results:
- OK - The sensor is receiving the correct supply voltage. Proceed to Test Step 5.
- Not OK - The correct supply voltage is not reaching the sensor.
Repair: Proceed to Troubleshooting, "Digital Sensor Supply Circuit - Test".
Stop.
Test Step 5. Check the Isolated Signal Frequency and the Duty Cycle at the Sensor
- Remove the wire from the harness side of P403:C (Throttle Signal).
- Turn the keyswitch to the ON position.
- Measure the frequency and the duty cycle between terminal B (Digital Sensor Return) and terminal C (Throttle Signal) at the J403/P403 breakout while you operate the throttle lever.
- Turn the keyswitch to the OFF/RESET position.
- Reinstall the wire in P403:C (Throttle Signal).
Expected Result:
The frequency should be between 150 and 1000 Hz. The duty cycle should be between 10 and 22 percent when the lever is moved to the low idle position. The duty cycle should be between 75 and 90 percent when the lever is moved to the high idle position.
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 sensor for the throttle signal.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 and the J403/P403 sensor for the throttle signal connector.
- Measure the following resistances:
- P403:A (+ Batt) to P403:B (Digital Sensor Return)
- P403:A (+ Batt) to P403:C (Throttle Signal)
- P403:B (Digital Sensor Return) to P403:C (Throttle Signal)
- P403:A (+ Batt) to P403:B (Digital Sensor Return)
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 | g00984617 |
ECM connector P1 | |
- Fabricate a jumper wire with pins at both ends.
- Use the jumper wire to short P403:A (+ Batt) and P403:C (Throttle Signal) together.
- Measure the resistance between P1:66 (Throttle Signal) and P1:48 (+ Batt).
- Move the one end of the jumper wire from P403:A (+ Batt) to P403:B (Digital Sensor Return). Leave the other end in P403:C (Throttle Signal).
- Measure the resistance between P1:66 (Throttle Signal) and P1:5 (Digital Sensor 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
- Remove the signal wire from J1:66 (Throttle Signal).
- Turn the keyswitch to the ON position.
- Measure the frequency and the duty cycle between the signal wire and the ECM ground strap while you operate the throttle lever.
- Turn the keyswitch to the OFF/RESET position.
- Reinstall the signal wire in J1:66.
Expected Result:
The frequency should be between 150 and 1000 Hz. The duty cycle should be between 10 and 22 percent when the lever is moved to the low idle position. The duty cycle should be between 75 and 90 percent when the lever is moved to the high idle position.
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 an Electronic Service Tool
- Turn the keyswitch to the ON position.
- Observe the status for "throttle signal" on the electronic service tool while you operate the throttle lever.
Expected Result:
The status should read approximately 0 percent when the throttle is moved to the low idle position. The status should progressively increase to 100 percent when the throttle lever is moved to the high idle position.
Note: This range can change depending on the adjustment of the throttle lever.
Results:
- OK - The sensor for the throttle signal 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.