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Headlamp Relay Testing

WARNING: This page is about a different car, the 2007 Pontiac Torrent and 2007 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the headlamp relay.
  2. Ignition ON, verify the headlamps are deactivated.
    • If the headlamps are still activated, repair the relay switch control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the relay coil 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 relay.
  4. Verify that a test lamp illuminates between the relay switch voltage supply circuit and ground.
    • If the test lamp does not illuminate, repair the relay switch voltage supply circuit for a short to ground or an open/high resistance. If the relay switch voltage supply circuit fuse is open, test the relay switch control circuit for a short to ground.
  5. Test for less than 1 ohm of resistance between the relay switch circuit ground and ground
    • If greater than 1 ohm, test the ground circuit for an open/high resistance
  6. Connect a 15-amp fused jumper wire between the relay switch voltage supply circuit and the relay switch control circuit. Verify the headlamps are activated.
    • If the headlamps are not activated, test the relay switch control circuit for an open/high resistance. If the circuit tests normal, test or replace the headlamp switch.
  7. Connect a test lamp between the relay coil control circuit and the relay coil voltage supply circuit.
  8. Command the headlamp relay ON and OFF by placing the headlamp switch in the AUTO position and covering and uncovering the ambient light sensor. 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 relay coil control circuit. If the circuit tests normal, replace the BCM.
    • If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the relay coil control circuit. If the circuit tests normal, replace the BCM.
  9. If all circuits test normal, test or replace the headlamp relay.
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