GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

Except RPO AXC/AXA

The key cylinder unlock feature will unlock all of the doors when the body control module (BCM) receives a Key Unlock Switch signal for greater than 1 second and will unlock all of the doors.

RPO AXC/AXA

The key cylinder unlock feature will unlock all of the doors when the driver door module (DDM) receives a Key Unlock Switch signal for greater than 1 second and will send a request to the passenger door module (PDM) and the BCM to unlock all of the doors.

Reference Information

Schematic Reference

Door Lock/Indicator Schematics

Connector End View Reference

Vehicle Access Connector End Views

Description and Operation

Power Door Locks Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification

Ignition OFF, insert the key into the driver’s door lock cylinder, turn the key clockwise and hold for greater than 1 second and turn the key counterclockwise and hold for greater than 1 second while observing the scan tool Door Key Cyl Unlock Switch parameters, the reading should change between Active and Inactive.

Circuit/System Testing

Except RPO AXC/AXE

  1. Ignition OFF, disconnect the harness connector at the driver door latch assembly.
  2. Test for less than 1.0 ohm between the ground circuit terminal 8 and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Door Key Cyl Unlock Switch parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal 9 for a short to ground. If the circuits test normal, replace the BCM.
  6. Install a 3-amp fused jumper wire between the signal circuit terminal 9 and ground, verify the scan tool Door Key Cyl Unlock Switch parameter is Active.
  7. If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. If all circuits tests normal, test or replace the driver door latch assembly.

With RPO AXC/AXE

  1. Ignition OFF, disconnect the harness connector at the driver door latch assembly.
  2. Ignition ON, verify the scan tool Door Key Cyl Unlock Switch parameter is Inactive.
  3. If not the specified value, test the signal circuit terminal 9 for a short to ground. If the circuits test normal, replace the DDM.
  4. Install a 3-amp fused jumper wire between the signal circuit terminal 9 and ground, verify the scan tool Door Key Cyl Unlock Switch parameter is Active.
  5. If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the DDM.
  6. Install a 3-amp fused jumper wire between the signal circuit terminal 9 and the low reference circuit terminal 8, verify the scan tool Door Key Cyl Unlock Switch parameter is Active.
  7. If not the specified value, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the DDM.
  8. If all circuits tests normal, test or replace the driver door latch assembly.

Component Testing

  1. Ignition OFF, disconnect the harness connector at the driver door latch assembly.
  2. Test for infinite resistance between the signal terminal 9 and the ground terminal 8 with the switch in the open position.
  3. If not the specified value, replace the driver door latch assembly.
  4. Test for less than 2.0 ohms between the signal terminal 9 and the ground terminal 8 with the switch in the Unlock position.
  5. If greater than the specified range, replace the driver door latch assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Door Lock Cylinder Replacement
    •  Front Side Door Latch Replacement
    •  Control Module References for BCM and DDM replacement, setup and programming