Circuit/System Testing
WARNING: This page is about a different car, the 2007 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, remove the horn relay.
- Ignition ON, verify that a test lamp illuminates on the coil side and switch side of the relay when connected between the horn relay supply voltage circuit and ground.
- If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance.
- Verify that the horn sounds with a 15-amp fused jumper connected between the horn relay supply voltage circuit and the horn control circuit.
- If the horn does not sound, test for an open or high resistance on the horn control circuit and the horn ground circuit. If the circuit/connections test normal replace the horn assembly.
- Disconnect the horn switch connector and ground the horn relay control circuit.
- Verify that a test lamp illuminates when connected between the horn relay supply voltage circuit and the horn relay control circuit.
- If the test lamp does not illuminate, test for a short to voltage, open or high resistance in the steering wheel coil assembly and the horn relay control circuit. If the circuit/connections test normal replace the body control module (BCM).
- Test or replace the horn relay.