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Courtesy Lamps Malfunction - All

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X4 harness connector at the BCM.
  2. Ignition ON, verify that a test lamp illuminates between the BCM 3 fuse voltage supply circuit terminal 2 and ground.
    • If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance.
  3. Ignition OFF, reconnect the X4 harness connector at the BCM.
  4. Ignition OFF, disconnect the harness connector at the left footwell courtesy lamp.
  5. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground for an open/high resistance.
  6. Connect a test lamp between the courtesy lamp supply voltage circuit terminal A and the ground circuit terminal B.
  7. Command the courtesy lamps 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 is always OFF, test the courtesy lamp supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
    • If the test lamp is always ON, test the courtesy lamp supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  8. Ignition OFF, disconnect the harness connector at the right footwell courtesy lamp.
  9. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground for an open/high resistance.
  10. Connect a test lamp between the courtesy lamp supply voltage circuit terminal A and the ground circuit terminal B.
  11. Command the courtesy lamps 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 is always OFF, test the courtesy lamp supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
    • If the test lamp is always ON, test the courtesy lamp supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM.
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