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| Illustration 1 | g01441739 |
Schematic for the 8 V supply | |
This diagnostic code is recorded when the ECM reads the voltage of the 8 volt DC supply circuit (wire X800-OR) and the voltage is below normal.
Note: 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 connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.
System Response:
Components that receive power from the 8 volt DC supply will not be available.
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 connector of the ECM from contact J1-44 (8 volt DC supply) to contact J1-45 (ground). Use the 7X-1710 Cable 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 8 volt DC supply voltage is correct. Verify that the diagnostic code is present. If the diagnostic code is still present the ECM has failed. Proceed to test step 2.
- NOT OK - Voltage is NOT 8.0 ± 0.5 DCV. The voltage is less than 8.0 ± 0.5 DCV. The ECM may have failed.
Repair: Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
Test Step 2. CHECK FOR A SHORT TO GROUND.
- Disconnect any sensor that uses the 8 volt DC supply voltage from the machine harness.
- At the harness connector for the ECM, measure the resistance between frame ground and contact J1-44 of the 8 volt DC supply circuit.
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. The harness circuit resistance is correct. The ECM may have failed.
Repair: Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NOT OK - The resistance is less than 5000 ohms with all the sensors disconnected from the machine harness. The machine harness is shorted to ground. Proceed to Test Step 3.
Test Step 3. DISCONNECT THE HANDLE.
- Turn the key start switch and the disconnect switch to the ON position.
- After disconnecting the handle, check the Caterpillar Electronic Technician (ET) for any active diagnostic codes.
Expected Result:
The diagnostic code changes from a FMI 04 to a FMI 03.
Results:
- OK - The diagnostic code changes to an FMI 03. There is an internal failure in the handle. The handle has failed.
Repair: Replace the handle.
STOP
- NOT OK - The diagnostic code does not change to an FMI 03. The ECM may have failed.
Repair: Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP