TH31-C9I, TH31-C9P, TH31-C9T, TH35-C11I, TH35-C13I, TH35-C13T, TH35-C15I and TH35-C15T Petroleum Power Train Packages and TH31-E61 and TH35-E81 Petroleum Transmissions Power Train Electronic Control System Caterpillar

Illustration 1	g01248848
Schematic of the +8V Supply

CID 0041 FMI 03 service code is recorded when the ECU reads the voltage of the 8 volt DC supply circuit (wire 709-OR) as higher than the normal voltage.

The following causes could signal this diagnostic trouble code:

• The 8 volt DC supply circuit (wire 709-OR) is shorted to the +battery circuit.

• The ECU has failed. This is unlikely.

Note: Ensure that the CID 0041 FMI 03 is active.

Note: Use a digital multimeter for the measurements in this procedure.

System Response:

Components that receive power from the 8 volt DC supply will not be available.

Test Step 1. CHECK THE HARNESS FOR A SHORT TO THE +BATTERY CIRCUIT.

1. The disconnect switch and the key start switch remain in the ON position.

2. Without disconnecting the harness, disconnect pin J1-44 from the ECU.

3. At the harness side of the connector for the ECU, measure the voltage from connector contact J1-44 (8 volt DC 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.

  STOP

Test Step 2. CHECK FOR THE CORRECT VOLTAGE AT THE ECU.

1. Turn the disconnect switch and the key start switch to the ON position.

2. Check the voltage at the connector of the ECU from contact J1-44 (8 volt DC supply) to contact J2-22 (sensor ground). Use the 7X-1710 Cable probes to measure the voltage. Do NOT disconnect the machine harness from the ECU. Wiggle the connector to make sure there is a strong connection.

Expected Result:

The voltage is 8.0 ± 0.5 DCV.

Results:

• OK - Voltage is 8.0 ± 0.5 DCV. The 8 volt DC supply voltage is correct. Verify that the diagnostic trouble code is present. If the diagnostic trouble code is still present, the ECU may have failed. Replace the ECU.

  Repair: Check the circuit again. Use the Caterpillar Electronic Technician (ET) service tool, if available, in order to perform a "Wiggle Test" on the machine wiring harness. The wiggle test can detect momentary or intermittent shorts or opens in the machine wiring harness. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic trouble code is not found, replace the ECU. Prior to replacing an ECU, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace".

  STOP

• NOT OK - Voltage is greater than 8.0 ± 0.5 DCV. The 8 volt DC supply voltage is NOT correct. The ECU has failed.

  Repair: Check the circuit again. Use the Caterpillar Electronic Technician (ET) service tool, if available, in order to perform a "Wiggle Test" on the machine wiring harness. The wiggle test can detect momentary or intermittent shorts or opens in the machine wiring harness. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic trouble code is not found, replace the ECU. Prior to replacing an ECU, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace".

  STOP