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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1548 (Lighting System) >> Diagnostic Information and Procedures >> Backup Lamps Malfunction (Automatic Transmission) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
  2. Ignition OFF, exterior lamps OFF, test for less that 5.0 Ω between the ground circuit terminal N5 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect the X2 harness connector at the underhood fuse block. Disconnect the X5 harness connector at the underhood fuse block.
  4. Connect a test lamp between the control circuit terminal H8 and ground.
  5. Command the Backup 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 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 an open/high resistance. If the circuit tests normal, replace the BCM.
  6. Ignition OFF, connect the X5 harness connector at the underhood fuse block. Disconnect the harness connector at the appropriate backup lamp.
  7. Ignition OFF, exterior lamps OFF, test for less than 5.0 Ω between the ground circuit terminal GRD and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect a test lamp between the control circuit terminal MJR and ground.
  9. Command the Backup 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 ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block.
    • If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
    • If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.
  10. If all circuits test normal, replace the backup lamp.
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