POUCH- 6V7784 - Caterpillar

Illustration 1 g00566286
Schematic of the relay (brake light)This diagnostic code is associated with the relay (brake light). The FMI 03 means that the ECM has determined that the voltage of the relay circuit is above normal. The possible causes of the diagnostic code are listed:
The relay has failed.
The energize circuit of the relay is shorted to the +battery circuit.
The ECM has failed. This is unlikely.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 0742 FMI 03 is active before performing this procedure.Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.Test Step 1. CHECK THE ENERGIZE CIRCUIT OF THE RELAY FOR A SHORT TO THE +BATTERY CIRCUIT.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connectors from the relay and the ECM.
At the machine harness connector for the ECM, measure the resistance from contact J2-40 (wire 958-YL) to all contacts that are used in the machine harness connectors for the ECM. Expected Result:Each resistance measurement is greater than 5000 ohms. Results:
OK - Each resistance measurement is greater than 5000 ohms. The machine harness is correct. Proceed to Test Step 2.
NOT OK - Each resistance measurement is not greater than 5000 ohms. There is a short in the machine harness. The short is between J2-40 (958-YL) and the circuit that has a low resistance measurement. Repair: Repair the machine harness or replace the machine harness. Stop.Test Step 2. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE.
Inspect the contacts and clean the contacts of the harness connectors.
Reconnect all harness connectors.
Turn the disconnect switch and the key start switch to the ON position.
Operate the machine.
Determine if the CID 0742 FMI 03 is active.Expected Result:The CID 0742 FMI 03 is active.Results:
YES - The CID 0742 FMI 03 is active. The problem has not been corrected. The ECM may have failed.Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace". Stop.
NO - The CID 0742 FMI 03 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. Stop.