Circuit/System Testing
WARNING: This page is about a different car, the 2009 GMC Canyon and 2009 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.
Headlamp Relay Control Circuit Test
- Ignition OFF, disconnect the HDLP relay.
- Connect a test lamp between the relay control circuit terminal 86 and B+.
- Ignition ON, command the headlamps ON and OFF with a scan tool. The test lamp should turn ON and OFF.
- 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 all circuits test normal, test or replace the relay.