Circuit/System Testing

Headlamp High Beam Light Bulb Circuit Testing 

1. Ignition OFF, disconnect the harness connector at the headlamp high beam light bulb terminal pin 3.
2. Ignition ON, verify that a test lamp illuminates between the headlamp high beam voltage supply circuit and ground.
   • If the test lamp does not illuminate, repair the voltage supply circuit for a short to ground or an open/high resistance. If the voltage supply circuit fuse is open, test or replace the headlamp high beam light bulb.
3. Connect a test lamp between the control circuit and the voltage supply circuit.
4. Command the headlamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
   • If the test lamp remains ON all the time, test for a short to ground on the control circuit.
   • If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit.
5. If all circuits test normal, test or replace the headlamp high beam light bulb.

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.
   • 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.
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.
5. If all circuits test normal, test or replace the headlamp switch, part of the multifunction switch.