Circuit/System Testing

Multifunction/Headlamp Switch Circuit Testing 

1. Ignition OFF, disconnect the harness connector at the headlamp switch terminal C1 pins 4 and 2.
2. Test for less than 1 Ω of resistance between the ground circuit and ground, terminal C1 pin 1.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Verify the headlamps are OFF.
   • If the headlamps are not OFF, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3-amp fused jumper wire between the signal circuit and ground. Verify the headlamps are ON.
   • If the headlamps are not ON, test the signal circuit of the headlamp switch for a short to voltage or an open/high resistance. If circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the headlamp switch which is part of the turn signal multifunction switch.

Headlamp Relay Circuit Testing 

1. Ignition OFF, disconnect the high and low beam headlamp relay terminals, C2 pin 18, C2 pin 8, C3 pin 9 and, C3 pin 21.
2. Ignition ON, verify the headlamps are deactivated.
   • If the headlamps are still activated, repair the relay switch control circuit for a short to ground, terminals C3 pin 9 and, 21.
3. Connect a test lamp between the relay coil control circuit, terminals C2 pins 8 and 18 and the underhood fuseblock B+ supply circuit.
4. Turn the headlamps ON by the headlamp switch. The test lamp should turn ON.
   • If the test lamp remains ON all the time, test for a short to ground on the relay coil control circuit. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the underhood fuseblock.