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

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

L/GATE RELSE Relay Switch B+

2

2

--

--

Liftgate Release Switch Signal

1

1

1

--

Liftgate Release Relay Control

2

2

2

--

L/GATE RELSE Relay Controlled Output Circuit

2

2

--

--

Rear Access Panel Relay Controlled Output Circuit

2

2

2

--

Rear Access Panel Switch Ground

--

1, 2

1, 2

--

Rear Access Panel Relay Block Ground

--

2

2

--

L/GATE RELSE Ground

--

2

2

--

1. Rear Access Panel Switch Inoperative

2. Rear Access Panel Release Inoperative

Circuit/System Description

The rear access panels can be released by pressing the rear access panel switches. The front doors must be unlocked, the transaxle must be in park or a vehicle with a manual transaxle, the vehicle must be stationary for the rear access panels to release.

The access panel release system consists of a primary relay, three secondary relays, three diodes, three release switches and three latches. When the appropriate release switch is pressed, the liftgate release signal circuit to the body control module (BCM) is grounded, the BCM detects a drop in voltage and the BCM enables the access panel release system by supplying voltage to the L/GATE RELSE relay coil. With the relay energized, battery positive voltage is allowed from the relay switched input through the switch contacts and out the relay switched output to the access panel release system and to the appropriate access panel/liftgate relay and latch. The release switch, when pressed, simultaneously provides a ground for the appropriate coil side access panel/liftgate relay, a diode prevents feedback in the liftgate release switch signal circuit.

When the appropriate rear access panel relay is energized, a ground circuit is provided for the appropriate access panel latch through the relay switch ground circuit allowing current to flow through the appropriate rear access panel latch and releasing the appropriate rear panel. Ground for the rear access panel relays is provided by G301.

Reference Information

Schematic Reference

Release Systems Schematics

Connector End View Reference

Vehicle Access Connector End Views

Description and Operation

Access Panel 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

  1. Ignition ON, observe the operation of the liftgate while pressing the Liftgate Release Switch. The liftgate should release.
  2. If the liftgate does not release, refer to Liftgate Release Inoperative .
  3. Observe the scan tool Liftgate Release Sw parameter while pressing and releasing the appropriate rear access panel switch. The reading should change between Active and Inactive.
  4. If the reading does not change between specified values, refer to Access Panel Switch Malfunction.
  5. Observe the operation of the appropriate rear access panel while pressing the appropriate rear access panel switch. The appropriate rear access panel should release.
  6. If the appropriate rear access panel does not release, refer to Rear Access Panel Release Malfunction.

Circuit/System Testing

Access Panel Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate Rear Access Panel Switch.
  2. Ignition OFF, test for less than 1 ohm for resistance between the ground circuit terminal A 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 Liftgate Release Sw parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.
  6. Install a 3A fused jumper wire between the signal circuit terminal C and ground. Verify the scan tool Liftgate Release Sw 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 test normal, test or replace the appropriate Rear Access Panel Switch.

Access Panel Release Malfunction

  1. Ignition OFF, disconnect the appropriate Rear Access Panel relay.
  2. Ignition OFF, test for less than 1 ohm between the relay switch ground circuit terminal and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the appropriate Rear Access Panel relay control circuit terminal and ground while pressing the appropriate Rear Access Panel Switch.
  5. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  6. Connect a test lamp between the relay coil control circuit terminal and B+.
  7. Press and release the appropriate rear access panel switch. The test lamp should turn ON and OFF.
  8. If the test lamp is always ON, test the relay coil control circuit for a short to ground.
    If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance.
  9. Connect the appropriate Rear Access Panel relay.
  10. Disconnect the appropriate rear access panel latch.
  11. Verify that a test lamp illuminates between the appropriate B+ circuit terminal and ground while pressing the appropriate liftgate release switch.
  12. • LR Access Panel Latch: terminal 3
    • RR Access Panel Latch: terminal 8
    If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  13. Connect a test lamp between the appropriate control circuit terminal and B+.
  14. • LR Access Panel Latch: terminal 4
    • RR Access Panel Latch: terminal 9
  15. Press and release the appropriate rear access panel switch. The test lamp should turn ON and OFF.
  16. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, test or replace the appropriate Rear Access Panel relay.
    If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, test or replace the appropriate Rear Access Panel relay.
  17. If all circuits test normal, test or replace the appropriate rear access panel latch.

Component Testing

Rear Access Panel Latch

  1. Ignition OFF, disconnect the harness connector at the appropriate Rear Access Panel Latch.
  2. Install a 20-amp fused jumper wire between the control circuit terminal 3 and 12 volts. Install a jumper wire between the ground circuit terminal 4 and ground. Verify the access panel latch activates.
  3. If the actuator does not perform as specified, replace the Rear Access Panel Latch.

Rear Access Panel Switch

  1. Ignition OFF, disconnect the harness connector at the appropriate Rear Access Panel switch.
  2. Test for infinite resistance between the signal terminal C and the ground circuit terminal A with the switch in the open position.
  3. If not the specified value, replace the appropriate Rear Access Panel switch.
  4. Test for less than 2 ohms between the signal terminal C and the ground circuit terminal A with the switch in the closed position.
  5. If greater than the specified range, replace the appropriate Rear Access Panel switch.

Relay Test

  1. Ignition OFF, disconnect the appropriate relay.
  2. Test for 60-180 ohms between terminals 85 and 86.
  3. If the resistance is not within the specified range, replace the relay.
  4. Test for infinite resistance between the following terminals:
  5. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    If not the specified value, replace the relay.
  6. Install a 20-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
  7. If greater than the specified range, replace the appropriate relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Control Module References for BCM replacement, setup and programming