Conditions Which Generate This Code:
Schematic of the 8 Volt Power Supply
The 8 V power supply provides the power for all 8V sensors.
The CID 0041 FMI 04 service code is activated when the ECM detects that the voltage of the 8 V power supply circuit is lower than normal.
The following causes could signal this diagnostic code:
- A sensor has failed.
- The power supply circuit is shorted to a ground source.
- The ECM has failed. This is unlikely.
Note: The following test procedure may create other diagnostic codes. Clear the diagnostic codes when the problem has been correct. Verify that CID 0041 FMI 04 is active before performing this procedure.
A level 2 warning is generated. Unexpected Motor Speed Detection will be disabled. While the machine is NOT in neutral, a level 3 warning will indicate Unexpected Motor Speed Detection Disabled. Since the throttle position sensor will be disabled, Underspeed control will be disabled. The Auxiliary Circuit will be disabled (if thumbroller is installed).
Test Step 1. CHECK THE SENSOR
- Turn the key start switch to the OFF position.
- One at a time, disconnect each sensor from the machine harness.
- After disconnecting each sensor, check to see if the CID 041 FMI 04 code is still active.
- Reconnect the sensor and disconnect the next sensor. Check to see if the CID 041 FMI 04 code is still active.
- Repeat the previous step until all sensors have been checked.
The diagnostic code is not active when a sensor is disconnected.
- OK - The diagnostic code is not active when a sensor is disconnected. Inspect the harness to the sensor for any failures. Disconnecting the sensor could temporarily cause the short to be removed from the harness. Reconnect the suspect sensor and verify that the diagnostic code has become active again.
Repair: Repair the harness or replace the sensor accordingly.
- NOT OK - The diagnostic code is still active. The machine harness may be shorted to ground. Proceed to Test Step 2.
Test Step 2. CHECK FOR A SHORT TO GROUND
- Disconnect the negative battery cable and turn the key start switch to the OFF position.
- Disconnect the machine harness connector J1 from the ECM.
- At the harness connector for the ECM, measure the resistance between contact J1-44 (wire P769-YL) and all other contacts that are used in the J1 and J2 connectors.
The resistance is greater than 5000 ohms.
- OK - The resistance is greater than 5000 ohms. The harness circuit resistance is correct. Proceed to Test Step 3.
- NOT OK - The resistance is less than 5000 ohms. The machine harness has failed.
Repair: The P769-YL wire is shorted to ground in the machine harness. Refer to the complete Electrical System Schematic for your machine. Check all harness connectors that are in the power supply circuit. Ensure that the connectors are clean and secure. Repair the machine harness or replace the machine harness.
Test Step 3. CHECK THE POWER SUPPLY AT THE ECM
- The key start switch remains in the OFF position.
- At ECM connector J1, use a 151-6320 Removal Tool to remove the supply wire and socket at contact J1-44 (wire P769-YL) and the return wire and socket at contact J1-45 (wire P770-WH) from the connector. The harness connector J1 remains connected to the ECM.
- Reconnect the negative battery cable and turn the key start switch to the ON position.
- At ECM connector J1, measure the voltage at the ECM pins between the power supply contacts J1-44 and J1-45.
The voltage measurement is 8.0 ± 0.5 DCV.
- OK - The voltage measurement is 8.0 ± 0.5 DCV. The voltage is correct. The ECM power supply is correct. Install the wires and sockets that were removed from the J1 connector back to their original locations. Proceed to Test Step 4.
- NOT OK - The voltage measurement is greater than 8.0 ± 0.5 DCV. The ECM power supply is not correct.
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 requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
Test Step 4. CHECK THE STATUS OF THE DIAGNOSTIC CODE
- Inspect the harness connectors and clean the contacts of the harness connectors and check the wires for damage to the insulation that is caused by excessive heat, corrosion, or chafing.
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the sensor circuit.
- Reconnect all harness connectors. Make sure that the connectors are fully seated and the clips for each connector are fastened.
- The key start switch remains in the ON position.
- Operate the machine.
- Determine if the CID 0041 FMI 04 diagnostic code is active.
The CID 0041 FMI 04 diagnostic code is active.
- YES - The CID 0041 FMI 04 diagnostic code is active. The problem has not been corrected.
Repair: Check the circuit again. If the cause of the problem is not found, contact the Technical Communicator for your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
- NO - The CID 0041 FMI 04 diagnostic code is not active. The problem does not exist at this time.
Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.