GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using the 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

The liftgate module receives an input from both the liftgate and liftglass ajar switches. The ajar switches are normally open when the liftgate and the liftglass are fully closed. When either the liftgate or liftglass is opened, the appropriate ajar switch contacts close providing a path to ground. The driver information center (DIC) located at the bottom of the instrument panel cluster (IPC), illuminates the rear access open message or the GATE AJAR indicator when either the glass or the gate is open. The IPC receives a class 2 serial data message from the liftgate module indicating the liftgate or liftglass ajar status. If this message is displayed and the vehicle speed is greater than 8.1 km/h (5 mph), a chime will sound.

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Displays and Gages Connector End Views

Electrical Information Reference

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

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

  1. Ignition OFF, disconnect the appropriate liftgate or liftglass ajar switch.
  2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.
  3. If greater than 1 ohm, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Liftgate Ajar Switch parameter or the Liftglass Ajar Switch parameter is Closed.
  5. If not Closed, test the appropriate signal circuit for a short to ground. If the circuit tests normal, replace the liftgate module.
  6. Ignition ON, check to see that the rear access open message or the gate ajar indicator is not displayed.
  7. If the message is displayed in the DIC or the indicator is illuminated, replace the IPC.
  8. Ignition ON, install a 3-amp fused jumper wire between the appropriate signal circuit and ground. Verify the scan tool Liftgate Ajar Switch parameter or the Liftglass Ajar Switch parameter is Ajar.
  9. If not Ajar, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal replace the liftgate module.
  10. Ignition ON, check to see that the rear access open message is displayed or the gate ajar indicator is illuminated.
  11. If the message is not displayed in the DIC or the indicator is not illuminated, replace the IPC.
  12. If all circuits test normal, test or replace the liftgate ajar switch or the liftglass ajar switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for liftgate module and IPC replacement, setup, and programming