This test should be used for troubleshooting opens and/or shorts in any of the engine sensor circuits that are shown in Illustration 1. These sensors provide various signals to the engine ECM. The analog sensors receive a regulated voltage supply of 5 VDC from the ECM. The digital sensors receive a regulated voltage supply of 8 VDC from the ECM.
Note: Refer to Troubleshooting, "Analog Sensor Supply Circuit - Test" if the ECM has detected a problem with the analog sensor supply voltage.
Note: Refer to Troubleshooting, "Digital Sensor Supply Circuit - Test" if the ECM has detected a problem with the digital sensor supply voltage.
The ECM performs an automatic calibration of these sensors whenever the ECM is powered and the engine is OFF for at least five seconds. During an automatic calibration, the ECM calibrates pressure sensors against the atmospheric pressure sensor and an acceptable offset pressure range.
Note: There are separate procedures for troubleshooting the fuel level sensor and the throttle position sensor. Refer to the appropriate topic in the "Troubleshooting with a Diagnostic Code" section of this manual.
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| Illustration 1 | g00794693 |
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 J2/P2 ECM connector, the J3/P3 machine connector, and all other connectors in the wiring harness. 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. All connections and grounds should be tight and free of corrosion.
Results:
- OK - Proceed to Test Step 2.
- Not OK -
Repair: Repair the circuit.Verify that the repair eliminates the problem.
Stop.
Test Step 2. Determine the Type of Sensor that is Suspect
Determine whether the suspect sensor is an analog sensor (+5 VDC) or a digital sensor (+8 VDC). Refer to Illustration 1.
Results:
- Analog (+5V) - Proceed to Test Step 3.
- Digital (+8V) - Proceed to Test Step 7.
Test Step 3. Check the Analog Sensor Supply Voltage at the Sensor Connector
- Disconnect the suspect sensor.
- Turn the keyswitch to the ON position.
- Use a multimeter to measure the voltage across terminal A (+5V Analog) and terminal B (Analog Return) at the harness side of the suspect sensor connector.
- Turn the keyswitch to the OFF/RESET position.
Expected Result:
The analog sensor supply voltage should be 5.0 ± 0.5 VDC.
Results:
- OK - The supply voltage is reaching the sensor. Proceed to Test Step 4.
- Not OK - The analog sensor supply voltage is not reaching the sensor.
Repair: Refer to Troubleshooting, "Analog Sensor Supply Circuit - Test" for the appropriate troubleshooting procedure.
Stop.
Test Step 4. Short the Sensor Signal at the Sensor Connector
- Turn the keyswitch to the OFF/RESET position.
- Connect ET to the service tool connector.
- Disconnect the suspect sensor from the harness.
- Turn the keyswitch to the ON position.
- Check the active diagnostic codes on ET.
Note: A diagnostic code with a FMI of "03" (Open/Short to +Battery) should be active for the disconnected sensor.
- Use a suitable piece of wire to short terminal B (Analog Return) and terminal C (Signal) at the harness side of the suspect sensor connector.
- Check the active diagnostic codes on ET.
Note: The diagnostic code should change to a "04" (Short to Ground) when the terminals are shorted.
Expected Result:
The FMI for the active diagnostic code should be "03" (Open/Short to +Battery) when the sensor is disconnected. The FMI should change to a "04" (Short to Ground) when the terminals are shorted.
Results:
- OK - The harness appears to be OK. The problem is with the sensor.
Repair: Replace the suspect sensor.Verify that the repair eliminates the problem.
Stop.
- Not OK - Proceed to Test Step 5.
Test Step 5. Measure the Resistance of the Signal Wire
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| Illustration 2 | g00755693 |
P2 ECM connector | |
- Disconnect the suspect sensor and the J2/P2 ECM connector.
- Measure the resistance between terminal C (Signal) at the harness side of the suspect sensor connector and the appropriate terminal for the sensor signal at the P2 ECM connector.
Expected Result:
The resistance through the signal wire should be less than 10 Ohms.
Results:
- OK - Proceed to Test Step 6.
- Not OK - There is an open circuit or excessive resistance in the signal circuit of the harness.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
Stop.
Test Step 6. Short the Sensor Signal at the ECM
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| Illustration 3 | g00751433 |
J2/P2 breakout | |
- Turn the keyswitch to the OFF/RESET position.
- Remove the suspect signal wire from the J2/P2 ECM connector.
- Install a 7X-1715 Adapter Cables (40 Pin Breakout) at the J2/P2 ECM connector.
- Turn the keyswitch to the ON position.
- Check the active diagnostic codes on ET.
Note: A diagnostic code with a FMI of "03" (Open/Short to +Battery) should be active for the sensor with the disconnected signal wire.
- Use a suitable piece of wire to short the terminal for the suspect sensor signal to P2:30 (Analog Sensor Return) at the breakout.
- Check the active diagnostic codes on ET.
Note: The diagnostic code should change to a "04" (Short to Ground) when the signal wire is shorted.
Expected Result:
The FMI for the active diagnostic code should change from a "03" (Open/Short to +Battery) to a "04" (Short to Ground) when the terminals are shorted.
Results:
- OK - There is a problem in the wiring between the suspect sensor and the ECM.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
Stop.
- Not OK - The ECM is not reading the sensor circuit.
Repair: Verify your results before replacing the ECM. Refer to Troubleshooting, "Replacing the ECM" before you replace the ECM.Verify that the repair eliminates the problem.
Stop.
Test Step 7. Check the Sensor Supply Voltage at the Sensor Connector
- Disconnect the suspect sensor.
- Turn the keyswitch to the ON position.
- Use a multimeter to measure the voltage across terminal A (+8V Digital) and terminal B (Digital Return) at the harness side of the suspect sensor connector.
- Turn the keyswitch to the OFF/RESET position.
Expected Result:
The digital sensor supply voltage should be 8.0 ± 0.5 VDC.
Results:
- OK - The supply voltage is reaching the sensor. Proceed to Test Step 8.
- Not OK - The digital sensor supply voltage is not reaching the sensor.
Repair: Refer to Troubleshooting, "Digital Sensor Supply Circuit - Test" for the appropriate troubleshooting procedure.
Stop.
Test Step 8. Check the Signal Wire for an Open
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| Illustration 4 | g00794975 |
P1 ECM connector | |
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| Illustration 5 | g00794976 |
P2 ECM connector | |
- Disconnect the suspect sensor and the appropriate ECM connector.
- Measure the resistance between terminal C (Signal) at the harness side of the suspect sensor connector and the appropriate terminal for the sensor signal at the ECM connector.
Expected Result:
The resistance through the signal wire should be less than 10 Ohms.
Results:
- OK - Proceed to Test Step 9.
- Not OK - There is an open circuit or excessive resistance in the signal circuit of the harness.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
Stop.
Test Step 9. Check the Signal Wire for a Short
- The suspect sensor and the appropriate ECM connector should already be disconnected.
- Check the resistance between the following terminals of the harness connector for the suspect sensor:
- C (Signal) to A (+8V Digital)
- C (Signal) to B (Digital Return)
- C (Signal) to A (+8V Digital)
Expected Result:
The resistance should be greater than 20,000 Ohms for each measurement.
Results:
- OK - The signal wire is good. Proceed to Test Step 10.
- Not OK - The signal wire is shorted.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
Stop.
Test Step 10. Install a New Sensor.
- Temporarily install a new sensor.
- Reconnect any connectors that have been disconnected in the troubleshooting process.
- Turn the keyswitch to the ON position.
- Check for diagnostic codes on ET.
- Turn the keyswitch to the OFF/RESET position.
Expected Result:
There are no active diagnostic codes for the suspect sensor.
Results:
- OK - Installing a new sensor fixed the problem.
Repair: Permanently install the new sensor.Verify that the repair eliminates the problem.
Stop.
- Not OK - Installing the new sensor did not fix the problem. The signal wire is good and the sensor is receiving the proper supply voltage.
Repair: Verify your results before replacing the ECM. Refer to Troubleshooting, "Replacing the ECM" before you replace the ECM.Verify that the repair eliminates the problem.
Stop.