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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 981 (Lighting Systems) >> Diagnostic Information and Procedures >> Exterior Courtesy Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Disconnect the harness connector at the affected courtesy lamp bulb.
  2. Ignition ON, verify that a test lamp illuminates between the courtesy lamp supply circuit terminal and ground.
    • If the test lamp does not illuminate, test the courtesy lamp supply circuit for a short to ground or an open/high resistance.
  3. Connect a test lamp between the low side control circuit terminal and the courtesy lamp supply circuit terminal.
  4. Command the Puddle/Courtesy Lamp 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 ON, test the control circuit for a short to ground. If the circuit tests normal, replace the door lock and side window switch.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the door lock and side window switch.
  5. If all circuits test normal, test or replace the affected bulb.
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