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.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Rear Access Panel Relay B+

2

2

--

--

Right Access Panel Release Signal

1,2

1

1

--

Left Access Panel Release Signal

1,2

1

1

--

Underhood Interlock Relay Control

B312A 02

B312A 05

B312A 05

--

LH Access Panel Relay Control

B250D 00

B250D 00

B250D 00

--

RH Access Panel Relay Control

B250E 00

B250E 00

B250E 00

--

Access Panel Latch Interlock Control

2

2

--

--

RH Access Panel Latch Control

2

2

2

--

LH Access Panel Latch Control

2

2

2

--

Rear Access Panel Switch Ground

--

1

1

--

Underhood Interlock Relay Ground

--

2

2

--

1. Rear Access Panel Switch Inoperative.

2. Rear Access Panel Latch Inoperative.

Circuit/System Description

The access panel release system consists of a interlock relay, 2 release relays, 3 release switches and 2 latches. When the appropriate release switch is pressed, the door request 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 ground to the appropriate door 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 appropriate access panel and latch.

Reference Information

Schematic Reference

Release Systems Schematics

Connector End View Reference

Component 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

Control Module References for scan tool information

Circuit/System Verification

  1. Ignition ON, observe the scan tool LR Access Panel Switch Status and RR Access Panel Switch Status parameters while pressing and releasing the rear access panel switches. The parameters should change between Active and Inactive.
  2. If the parameters do not change, refer to Access Panel Switch Malfunction.
  3. Observe the scan tool Rear Access Panel Lock Relay Cmd. parameter while pressing and releasing the rear access panel switches. The parameter should change between Active and Inactive.
  4. If the parameter does not change, refer to Access Panel Interlock Malfunction.
  5. Observe the operation of the rear access panels while using the rear access panel switches. The rear access panel latches should release the access panels.
  6. If both rear access panel latches do not release, refer to Access Panel Interlock Malfunction
    If a rear access panel latch 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. Test for less than 1 ohm 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 Access Panel Switch Status 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 Access Panel Switch Status 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 rear access panel switch.

Access Panel Interlock Malfunction

  1. Ignition OFF, disconnect the Door Lock relay.
  2. Test for less than 1 ohm between the relay coil ground circuit terminal and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Test for less than 1 ohm between the relay switch ground circuit terminal and ground.
  5. If greater than the specified range, test the ground circuit for an open/high resistance.
  6. Connect a test lamp between the relay coil control circuit terminal and the relay coil ground circuit terminal.
  7. Ignition ON, command the Rear Access Panel Lock Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  8. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the IPC.
    If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the IPC.
  9. Connect a test lamp between the access panel latch control circuit terminal and the relay switch ground circuit terminal.
  10. Command the access panel latches to RELEASE by pressing the rear access panel switch. The test lamp should illuminate while commanding the RELEASE state.
  11. If the test lamp does not illuminate, test the control circuit for short to ground or an open/high resistance.
  12. If all circuits test normal, test or replace the Door Lock relay.

Access Panel Release Malfunction

  1. Ignition OFF, disconnect the appropriate Rear Access Panel relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit terminal and ground.
  3. If the test lamp illuminates, test the output circuit for a short to voltage.
  4. Verify that a test lamp illuminates between the relay coil B+ circuit terminal and ground.
  5. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay controlled output circuit terminal for a short to ground. If the circuit tests normal, test or replace the Rear Access Panel relay.
  6. Verify that a test lamp illuminates between the relay switch B+ circuit terminal and ground.
  7. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  8. Disconnect the harness connector at the appropriate access panel latch.
  9. Test for less than 5 ohms between the control circuit terminal listed below and ground while commanding the Rear Access Panel Lock Relay ON with a scan tool.
  10. • Left rear access panel latch circuit terminal 4
    • Right rear access panel latch circuit terminal 9
    If greater than the specified range, test the control circuit for an open/high resistance.
  11. Connect the harness connector at the access panel latch.
  12. Connect a 20A fused jumper wire between the relay switch B+ circuit terminal and the relay controlled output circuit terminal.
  13. Verify the access panel latch is activated while commanding the Rear Access Panel Lock Relay ON with a scan tool.
  14. If the access panel latch does not activate, test the output circuit for an open/high resistance. If the circuit tests normal, test or replace the access panel latch.
  15. Connect a test lamp between the relay coil B+ circuit terminal and the relay coil control circuit terminal.
  16. Command the Rear Access Panel relay ON and OFF by pressing and releasing the rear access panel switch. The test lamp should turn ON and OFF when changing between the commanded states.
  17. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
  18. If all circuits test normal, test or replace the Rear Access Panel relay.

Component Testing

Rear Access Panel Actuator

  1. Ignition OFF, disconnect the harness connector at the appropriate access panel latch.
  2. Install a 20A fused jumper wire between the control circuit terminal and 12 volts of the access panel latch listed below:
  3. • Left rear access panel latch terminal 3
    • Right rear access panel latch terminal 8
  4. Install a jumper wire between the ground terminal and ground of the access panel latch listed below:
  5. • Left rear access panel latch terminal 4
    • Right rear access panel latch terminal 9
  6. Verify the access panel latch activates.
  7. If the latch 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 terminal A with the switch in the open position.
  3. If not the specified value, replace the rear access panel switch.
  4. Test for less than 2 ohms between the signal terminal C and the ground terminal A with the switch in the closed position.
  5. If greater than the specified range, replace the 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 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 relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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