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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1087 (Lighting Systems) >> Diagnostic Information and Procedures >> Park, License, and/or Tail Lamps Malfunction (European) >> Circuit/System Testing >> License Lamps Malfunction

License Lamps Malfunction

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 park lamp relay.
  2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the park lamp relay ground circuit terminal A1 and ground
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal A2 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  4. Ignition ON, park lamps ON, verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal A2 for a short to ground. If the circuit tests normal, test or replace the park lamp relay.
  5. Verify that a test lamp illuminates between the B+ circuit terminal C2 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  6. Disconnect the harness connector at the inoperative license lamp.
  7. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the inoperative license lamp ground circuit terminal 2 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect the harness connector at the inoperative license lamp.
  9. Connect a 10A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2.
  10. Ignition ON, park lamps ON, Verify the license lamps are activated.
    • If the license lamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the inoperative license lamp.
  11. If all circuits test normal, test or replace the park lamp relay.
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