The digital sensor supply provides 8.0 ± 0.5 VDC to the following sensors:
- Brake oil temperature sensor
- Coolant level sensor
- Throttle position sensor
- Torque converter oil temperature sensor
The digital sensor supply is output short circuit protected. The ECM is protected from a short to ground and a short to + battery condition. The digital sensors are NOT protected.
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| Illustration 1 | g00795455 |
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 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. Check for Shorts in the Harness from the ECM to the Digital Sensors
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| Illustration 2 | g00738799 |
ECM connector P1 | |
- Disconnect ECM connector J1/P1 and all of the digital sensors.
- Measure the resistance between P1:35 (Digital Sensor +8 VDC) and engine ground.
- Measure the resistance between P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return).
Expected Result:
The resistance should be greater than 20,000 Ohms for each measurement.
Results:
- OK - Proceed to Test Step 3.
- Not OK - There is a short between the ECM and one of the sensors.
Repair: Repair the circuit.
Stop.
Test Step 3. Check for Open Circuits in the Harness Between the ECM and the Digital Sensors
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| Illustration 3 | g00738799 |
J1/P1 breakout | |
- Turn the keyswitch to the OFF/RESET position and install a 7X-1715 Adapter Cable (40 Pin Breakout) at the J1/P1 ECM connector .
- Use a suitable piece of wire to short P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return) at the breakout.
- Disconnect all of the digital sensors.
- Measure the resistance between terminal A (+8 VDC) and terminal B (Digital Return) of the connector for each digital sensor.
- Remove the wire short from the breakout.
Expected Result:
The resistance should be less than 10 Ohms for each measurement.
Results:
- OK - Proceed to Test Step 4.
- Not OK - There is an open circuit in the wiring harness between the sensor and the ECM.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
Stop.
Test Step 4. Check the Digital Sensor Supply Voltage at the Sensor Connectors
- Disconnect all of the digital sensors.
- Turn the keyswitch to the ON position.
- Measure the voltage across terminal A (+8 VDC) and terminal B (Digital Return) of the connector for each digital sensor.
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 5.
- Not OK - The supply voltage is not reaching the sensor. Proceed to Test Step 7.
Test Step 5. Check the Digital Sensors for Internal Shorts
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| Illustration 4 | g00738799 |
J1/P1 breakout | |
- Disconnect all of the digital sensors.
- Turn the keyswitch to the ON position.
- Reconnect each of the digital sensors while you observe the voltage across P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return) at the breakout.
Expected Result:
The supply voltage should be 8.0 ± 0.5 VDC. The voltage should not drop when the sensors are connected.
Results:
- OK - None of the sensors are internally shorted.
Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.
Stop.
- Not OK - The sensor that caused the voltage to drop may have an internal short. Proceed to Test Step 6.
Test Step 6. Temporarily Install a New Sensor
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| Illustration 5 | g00738799 |
J1/P1 breakout | |
- Disconnect the suspect sensor and remove the suspect sensor.
- Temporarily install a new sensor.
- Turn the keyswitch to the ON position.
- Observe the voltage across P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return) at the breakout while you connect the new sensor.
Expected Result:
The supply voltage should be 8.0 ± 0.5 VDC. The voltage should not drop when the sensor is connected.
Results:
- OK - The suspect sensor was faulty.
Repair: Permanently install the new sensor.
Stop.
- Not OK - The sensor and the circuit appear to be OK at this time.
Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.
Stop.
Test Step 7. Check the Digital Sensor Supply Voltage at the ECM
| | |
| Illustration 6 | g00738799 |
J1/P1 breakout | |
- Disconnect all of the digital sensors.
- Turn the keyswitch to the ON position.
- Measure the voltage across P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return) at the breakout.
Expected Result:
The supply voltage should be 8.0 ± 0.5 VDC.
Results:
- OK - The ECM is supplying the correct voltage.
Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.
Stop.
- Not OK - The ECM is not supplying the correct voltage.
Repair: Verify your results.Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.Verify that the repair eliminates the problem.
Stop.