LINK & BEARING AS-BUCKET 2785943 - Caterpillar

Illustration 1 g02174303
Schematic of the 8V power supplyThe 8V power supply provides the power for the Auxiliary Thumbroller.The CID 0041 FMI 04 service code is activated when the ECM detects that the voltage of the 8V supply 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. The failure of the ECM 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.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 0041 FMI 04 code is still active.
Reconnect the sensor and disconnect the next sensor. Check to see if the CID 0041 FMI 04 code is still active.
Repeat the previous step until all sensors have been checked.Expected Result:The diagnostic code is not active when a sensor is disconnected.Results:
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.STOP
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 J1-68 (wire P994-BU) and all other contacts that are used in the J1 and J2 connectors. Expected Result:The resistance is greater than 5000 ohms.Results:
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 P994-BU 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.STOPTest 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 J1-68 (wire P994-BU) and the return wire and socket at contact J1-55 (wire P997-BR) 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 J1-68 and J1-55.Expected Result:The voltage