Circuit/System Testing
WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the door unlock relay.
- Connect a test lamp between the B+ circuit terminal 8 and the control circuit terminal 9.
- Command the rear door locks to LOCK and UNLOCK with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
- If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
- If the circuits test normal, test or replace the door unlock relay.