TUBE 2975443 - Caterpillar

Illustration 1 g01441739
Schematic for the 8 VDC supplyCID 0041 FMI 03 service code is recorded when the ECM reads the voltage of the 8 VDC supply circuit (wire X800-OR) as higher than the normal voltage. The following causes could signal this diagnostic code:
The 8 VDC supply circuit (wire X800-OR) is shorted to the +battery circuit.
The ECM may have failed. The failure of an ECM is unlikely.Note: Ensure that the CID 0041 FMI 03 is active.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 VDC supply will not be available. Test Step 1. CHECK THE HARNESS FOR A SHORT TO THE +BATTERY CIRCUIT.
The disconnect switch and the key start switch remain in the ON position.
Without disconnecting the harness, disconnect pin J1-44 from the ECM.
At the harness side of the connector for the ECM, measure the voltage from connector contact J1-44 (8 VDC supply) to frame ground.Expected Result:The voltage is 0.0 0.5 DCV.Results:
OK - The voltage is 0.0 0.5 DCV. The voltage is correct. Proceed to Test Step 2.
NOT OK - Voltage is NOT 0.0 0.5 DCV. The harness has failed.Repair: The machine harness is shorted to the +battery circuit. Repair the machine harness or replace the machine harness.STOPTest Step 2. CHECK FOR THE CORRECT 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 VDC supply) to contact J1-45 (ground). Use the 7X-1710 Multimeter Probe to measure the voltage. Do NOT disconnect the machine harness from the ECM. Wiggle the connector in order to make sure that there is a strong connection.Expected Result:The voltage is 8.0 0.5 VDC.Results:
OK - Voltage is 8.0 0.5 VDC. The 8 VDC supply voltage is correct. Verify that the diagnostic code is present. If the diagnostic code is still present, the ECM may have failed.Repair: Prior to replacing an ECM, always contact your 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 - Voltage is greater than 8.0 0.5 VDC. The 8 VDC supply voltage is NOT correct. The ECM may have failed.Repair: Prior to replacing an ECM, always contact your 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