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| Illustration 1 | g01447437 |
Connections of the 8 volt supply | |
This diagnostic code is associated with the power supply for the sensors. The FMI 04 means that the ECM has determined that the voltage of the sensor circuit is below normal.
The possible causes of the diagnostic code are listed:
- A sensor has failed.
- The supply circuit is shorted to ground.
- ECM has failed. This is unlikely.
Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all of the connections in the circuit are clean and secure. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.
Note: The following test procedure may create other diagnostic codes. Clear the diagnostic codes when the problem has been corrected. Verify that the CID 0041 FMI 04 is active before performing this procedure.
Use a digital multimeter for the measurements in this procedure.
System Response:
All of the sensors that receive power from the 8 volt supply are disabled.
Test Step 1. CHECK THE VOLTAGE AT THE ECM.
- Turn the disconnect switch and the key start switch to the ON position.
- Check the voltage at the harness connector for the ECM from contact J1-44 (wire X800-OR) to contact J1-45 (J764-BR). Use the multimeter probes to measure the voltage. Do NOT disconnect the machine harness from the ECM.
Expected Result:
The voltage is 8.0 ± 0.5 DCV.
Results:
- OK - The voltage is 8.0 ± 0.5 DCV. The sensor supply voltage is correct. Verify that the same diagnostic code is present. If the diagnostic code is still present the ECM may have failed.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Also, recheck if the diagnostic code is active. Prior to replacing and ECM, contact your dealership for possible consultation with Caterpillar. If the ECM requires replacing, see Troubleshooting, "Electronic Control Module (ECM) - Replace".
STOP
- NOT OK - The voltage is NOT 8.0 ± 0.5 DCV. The voltage is less than 8.0 ± 0.5 DCV. The sensor supply voltage is NOT correct. Proceed to Test Step 2.
Test Step 2. CHECK FOR A SHORT TO GROUND
- Turn the key start switch and the disconnect switch to the OFF position.
- Disconnect the machine harness from the ECM.
- At the harness connector for the ECM, measure the resistance between frame ground and contact J1-45 (wire J764-BR).
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. Verify that the same diagnostic code is present. If the diagnostic code is still present the ECM may have failed.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Also, recheck if the diagnostic code is active. Prior to replacing and ECM, contact your dealership for possible consultation with Caterpillar. If the ECM requires replacing, see Troubleshooting, "Electronic Control Module (ECM) - Replace".
STOP
- NOT OK - Resistance is less than 5 ohms. The machine harness has failed or a sensor has failed. Proceed to Test Step 3.
Test Step 3. DISCONNECT THE SENSORS.
- The key start switch and the disconnect switch remain in the OFF position.
- One at a time, disconnect any sensor that uses the power supply from the machine harness.
- After disconnecting each sensor, check the resistance from frame ground to contact J1-45 at the harness connector for the ECM.
Expected Result:
After disconnecting a particular sensor, the resistance changes and the resistance is greater than 5000 ohms.
Results:
- YES - After disconnecting a particular sensor, the resistance changes and the resistance is greater than 5000 ohms. The sensor that was just disconnected has failed.
Repair: Replace the sensor.
STOP
- NO - After disconnecting all of the sensors, the resistance is less than 5 ohms. The machine harness is shorted to ground.
Repair: Repair the machine harness or replace the machine harness.
STOP