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Circuit/System Testing

WARNING: This page is about a different car, the 2007 Cadillac XLR. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the rear fog lamp relay.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal B1 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the rear fog lamp relay control circuit terminal B2 and the ground circuit terminal B1.
  4. Command the rear fog lamps ON and OFF with the rear fog lamp switch. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    • If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the rear fog lamp relay.
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