FITTING 0306943 - Caterpillar

Illustration 1 g01192266
Schematic for the Backup AlarmThe ECM applies power to the backup alarm whenever the ECM receives a signal from the reverse direction switch.The possible causes for the backup alarm are listed:
The harness circuit is shorted.
The ECM has failed.Test Step 1. CHECK FOR A SHORTED HARNESS
Turn the disconnect switch to the OFF position.
Disconnect the harness connector from the ECM.
Disconnect the backup alarm from the harness.
At the harness connector for the ECM, measure the resistance between contact J1-12 (wire 321-BR) and all other possible sources of +battery.Expected Result:Each resistance should be 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. It is unlikely that the ECM has failed. Perform this Step again.Repair: If the cause is not found, replace the ECM. See Testing And Adjusting, "Electronic Control Module (ECM) - Replace". Stop.
NO - A resistance measurement is less than 5000 Ohms (continuity). The harness has failed. The corresponding wire is shorted to wire 321-BR within the harness.Repair: Repair the harness or replace the harness. Stop.