BRACKET 2337221 - Caterpillar

Illustration 1 g02645821
Schematic for the Backup AlarmThe ECM applies power to the backup alarm relay whenever the ECM receives a reverse signal from the shift lever.The possible causes for the backup alarm "always on" are listed below:
The harness circuit is shorted.
The relay is shorted
The ECM has failed.Test Step 1. CHECK FOR A SHORTED HARNESS
Turn the disconnect switch to the OFF position.
Unplug the backup alarm relay.
Disconnect the backup alarm and the backup lamps from the harness.
At the harness connector for the backup alarm, measure the resistance between contact 1 (wire 612-GY) and all other possible sources of +battery.Expected Result:Each resistance is greater than 5000 ohms.Results:
YES - All the resistance measurements are greater than 5000 Ohms (no continuity). The resistance to the harness circuit is correct. Proceed to Test Step 2.
NO - A resistance measurement is less than 5000 Ohms (continuity). The harness has failed. The corresponding wire is shorted to wire 331-OR within the harness.Repair: Repair the harness or replace the harness.STOPTest Step 2. CHECK FOR A SHORTED RELAY
Reconnect the relay. The backup alarm harness connector remains disconnected.
At the harness connector for the backup alarm, measure the resistance between contact 1 (wire 612-GY) and fuse G5.Expected Result:The resistance measurement is greater than 5000 ohms.Results:
YES - The resistance measurement is greater than 5000 ohms. The resistance of the harness through the relay is correct. Failure of the ECM is unlikely. Perform this step again.Repair: If the cause is not found, replace the ECM. See Troubleshooting, "Electronic Control Module (ECM) - Replace".STOP
NO - The resistance measurement is less than 5000 ohms. There is continuity through the relay. The relay is shorted.Repair: Replace the relay.STOP