DISC-YM 3676070 - Caterpillar

Illustration 1 g00778274
Schematic of the Backup Alarm CircuitThis diagnostic code is recorded when the ECM reads the voltage of the backup alarm circuit as being above normal.The possible causes for this diagnostic code are listed:
The circuit of the backup alarm is shorted to the +battery circuit.
The ECM has failed. This is unlikely.Note: Ensure that the CID 0637 FMI 03 for the backup alarm is on hold.Test Step 1. CHECK THE BACKUP ALARM CIRCUIT FOR A SHORT TO THE +BATTERY CIRCUIT.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the backup alarm.
Disconnect the machine harness connectors J1 and J2 from the ECM.
At machine harness connector J1 and J2, measure the resistance. Measure the resistance from the signal contact J2-55 (wire 321-BR) to all contacts that are used for the machine harness connectors of 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 - The resistance is NOT correct. There is a short in the machine harness. The short is between signal contact J2-55 (wire 321-BR) and the circuit with the low resistance measurement.Repair: Repair the harness or replace the harness.STOPTest Step 2. CHECK IF THE DIAGNOSTIC CODE REMAINS.
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.
Clear all logged diagnostic codes.
Operate the machine.
Observe the status of the diagnostic code for the backup alarm.Expected Result:The diagnostic code for the backup alarm is NOT present. Results:
YES - The diagnostic code is NOT present. The diagnostic code does not exist at this time. 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
NO - The diagnostic code has not been corrected. The ECM has failed.Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this diagnostic code 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