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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 >> Backup Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

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Backup Lamp Relay Control Circuit Test

  1. Ignition OFF, disconnect the harness connector X5 at the BCM.
  2. Ignition ON, vehicle in park, verify the backup lamps are not on.
    • If the backup lamps are on, test the backup lamp relay control circuit terminal11 for a short to voltage. If the circuit tests normal replace the underhood fuse block.
  3. Install a 10A fused jumper wire between the relay control circuit terminal 11 and battery voltage. Verify the backup lamps are on.
    • If the backup lamps are not on, test the backup lamp relay control circuit for an open/high resistance or short to gerund. If the circuit tests normal replace the underhood fuse block.
  4. If all circuits test normal, replace the BCM.

Backup Lamp Circuit Test

  1. Ignition OFF, disconnect the harness connector at the affected backup lamp.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal GRD and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Connect a test lamp between the control circuit terminal MJR and the ground circuit terminal GRD.
  4. 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, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
  5. If all circuits test normal, test or replace the affected backup lamp.
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