MUFFLER-YM 3607877 - Caterpillar

If the backup alarm is always off, one of the following problems may exist:
The backup alarm has failed.
The harness circuit is open.
The harness circuit is shorted to ground.
The ECM has failed.Test Step 1. CHECK THE BACKUP ALARM.
Disconnect the backup alarm from the machine harness.
Use jumpers to connect the respective terminals of the backup alarm to the +battery circuit and ground. Expected Result:The backup alarm sounds when power is applied.Results:
YES - The backup alarm operates correctly. Proceed to test step 2.
NO - The backup alarm has failed.Repair: Replace the backup alarm.STOPTest Step 2. CHECK THE CIRCUIT FOR THE BACKUP ALARM FOR A SHORT TO GROUND.
The machine harness remains disconnected from the backup alarm.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connectors J1 and J2 from the ECM.
At machine harness connector J2, measure the resistance from the J2-37 (backup alarm signal) to all possible sources of ground. The possible ground sources are connector contacts: J1-2, J1-5, J1-7, J1-15, J1-16, J2-3 and frame ground. Expected Result:Each resistance should be greater than 5000 ohms.Results:
OK - The machine harness is correct. Proceed to test step 3.
NOT OK - There is a short in the machine harness. The harness has failed.Repair: The short is between wire 321-BR(Brown) (backup alarm signal) and the circuit with the low resistance measurement. Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK THE CIRCUIT FOR THE BACKUP ALARM FOR AN OPEN.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the J1 and J2 machine harness connectors from the ECM.
At the machine harness connector for the backup alarm, place a jumper from contact 1 to contact 2.
At machine harness connector J2, measure the resistance from J2-37 (backup alarm signal) to J2-3 (return signal). Expected Result:The resistance that is measured is less than 5 ohms.Results:
OK - The machine harness is correct. Proceed to test step 4.
NOT OK - There is an open circuit in the machine harness. The harness has failed.Repair: The open is in wire 321-BR(Brown) (backup alarm signal) or in wire 975-WH(White) (return signal) of the machine harness. Repair the machine harness or replace the machine harness.STOPTest Step 4. CHECK IF THE PROBLEM IS STILL ACTIVE.
Inspect the contacts of the harness connector and clean the contacts of the harness connectors.
Reconnect all harness connectors.
Start the engine. Expected Result:The backup alarm works while the transmission lever is in REVERSE.Results:
YES - The problem is NOT present. Repair: The problem does not exist at this time. The initial problem 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 problem has not been corrected. The ECM has failed.Repair: Exit this procedure and perform the diagnostic code procedure again. If the problem persists, the ECM may have failed. Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may