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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 991 (Door Lock Systems & Door Handles) >> Diagnostic Information and Procedures >> Power Door Locks Inoperative - Front (w/o AN3) >> 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.

Door Lock Switch Circuit Test

  1. Disconnect the affected door lock switch and verify that the scan tool switch parameter displays Idle.
    • If the parameter displayed is Lock or Unlock test the affected switch signal circuit for a short to ground. If the circuit tests normal replace the BCM.
  2. Verify less than 1 ohm or resistance from the ground circuit terminal B to ground.
    • If the resistance is greater than the specified value repair the ground circuit for an open/high resistance.
  3. Connect a fused jumper wire from the lock switch signal circuit terminal D to ground and verify that the scan tool switch parameter displays Lock.
    • If the parameter displayed is not Lock test the lock switch signal circuit for an open/high resistance. If the circuit tests normal replace the BCM.
  4. Connect a fused jumper wire from the unlock switch signal circuit terminal E to ground and verify that the scan tool switch parameter displays Unlock.
    • If the parameter displayed is not Unlock test the unlock switch signal circuit for an open/high resistance. If the circuit tests normal replace the BCM.
  5. If the circuits test normal replace the affected door lock switch.

Door Lock Relay Control Circuit Test

  1. Verify that a test lamp connected to battery voltage illuminates when connected to the supply side of the lock 1 and 2 fuses in the IP fuse block.
    • If the test lamp does not illuminate test the lock/unlock relay ground circuit for an open/high resistance. If the circuit tests normal replace the IP fuse block.
  2. Disconnect the BCM connector X7.
  3. Verify that all of the door lock actuators lock when a fused jumper wire is connected to the door lock relay control circuit terminal 7 and briefly applied to battery voltage.
    • If all of the door lock actuators do not lock, test the door lock relay control circuit for an open/high resistance. If the circuit tests normal replace the IP fuse block.
    • If only the front or rear door lock actuators do not lock replace the IP fuse block.
  4. If the circuits test normal replace the BCM.

Driver Door Unlock Relay Control Circuit Test

  1. Verify that a test lamp connected to battery voltage illuminates when connected to the supply side of the DRV unlock fuse in the IP fuse block.
    • If the test lamp does not illuminate test the IP fuse block ground circuit for an open/high resistance. If the circuit tests normal replace the IP fuse block.
  2. Disconnect the BCM connector X7.
  3. Verify that the driver door lock actuator unlocks when a fused jumper wire is connected to the driver door unlock relay control circuit terminal 6 and briefly applied to ground.
    • If the driver door lock actuator does not unlock, test the driver door unlock relay control circuit for an open/high resistance. If the circuit tests normal replace the IP fuse block.
  4. If the circuits test normal replace the BCM.

Passenger Door Unlock Relay Control Circuit Test

  1. Verify that a test lamp connected to battery voltage illuminates when connected to the supply side of the unlock 1 and 2 fuses in the IP fuse block.
    • If the test lamp does not illuminate test the IP fuse block ground circuit for an open/high resistance. If the circuit tests normal replace the IP fuse block.
  2. Disconnect the BCM connector X7.
  3. Verify that all of the passenger door lock actuators unlock when a fused jumper wire is connected to the passenger door unlock relay control circuit terminal 9 and briefly applied to ground.
    • If the passenger door lock actuators do not unlock, test the passenger door unlock relay control circuit for an open/high resistance. If the circuit tests normal replace the IP fuse block.
  4. If the circuits test normal replace the BCM.

Door Lock Actuator Circuit Test

  1. Disconnect the affected door latch connector and connect a test lamp across the lock actuator control circuit terminals.
  2. Verify that the test lamp illuminates briefly when a lock and unlock switch is activated.
    • If the test lamp does not illuminate in both switch positions test the lock actuator control circuits for an open/high resistance or short to ground. If the circuits test normal replace the IP fuse block.
  3. If the circuits test normal replace the affected door latch.
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