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

Door Lock/Unlock Relay B+

1

1

--

--

Driver Door Lock Switch Lock Signal

B3150 00

B3150 00

B3150 00

--

Driver Door Lock Switch Unlock Signal

B3140 00

B3140 00

B3140 00

--

Passenger/Cargo Door Lock Switch Lock Signal

B3155 00

B3155 00

B3155 00

--

Passenger/Cargo Door Lock Switch Unlock Signal

B3145 00

B3145 00

B3145 00

--

Passenger/Cargo Unlock Relay Control

B3130 00

B3130 00

B3130 00

--

Driver Unlock Relay Control

B3125 00

B3125 00

B3125 00

--

Door Lock Relay Control

B3135 00

B3135 00

B3135 00

--

Cargo Unlock Relay Control

2

2

2

--

Door Lock Switch Ground

--

3

3

--

Door Lock/Unlock Relay Ground

--

1

1

--

1. All Latches Malfunction

2. Cargo Door Latch Malfunction

3. Door Lock Switch Malfunction

Circuit/System Description

When any of the door lock switches are placed in the lock position, a ground signal is applied to the BCM through the door lock signal circuit. Upon receiving this signal, the BCM grounds the control side of the door lock relay through the door lock relay control circuit. Since the other side of the door lock relay coil is connected to battery voltage, the relay is energized. This causes the contacts to close and complete the path from the battery voltage circuit. Voltage is then applied to the lock side of the door lock actuators through the door lock actuator lock circuits. Since the other side of the all the door lock actuators are connected to the normally closed contacts of their respective unlock relays to ground, the doors lock.

Reference Information

Schematic Reference

Door Lock/Indicator Schematics

Connector End View Reference

Component 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

Control Module References for scan tool information

Circuit/System Verification

  1. Ignition ON, observe the Driver Door Lock Sw and Driver Door Unlock Sw parameters while using the driver door lock switch. The parameter should change from Inactive to Active.
  2. If the value does not change between commanded states, refer to Driver Door Lock Switch Malfunction.
  3. Observe the Psgr Door Lock Sw and Psgr Door Unlock Sw parameters while using the passenger and cargo door lock switches. The parameter should change from Inactive to Active.
  4. If the value does not change between commanded states, refer to Passenger/Cargo Door Lock Switch Malfunction.
  5. Command the driver door and passenger door latches to LOCK and UNLOCK by using the door lock switch, the doors should perform LOCK and UNLOCK function.
  6. If the driver, passenger or cargo door latch does not LOCK or UNLOCK, refer to Door Lock Malfunction.
    If a sliding door latch does not LOCK or UNLOCK, refer to Sliding Door Lock Malfunction.

Circuit/System Testing

Driver Door Lock Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the driver door lock 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 Driver Door Lock Sw parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the BCM.
  6. Verify the scan tool Driver Door Unlock Sw parameter is Inactive.
  7. If not the specified value, test the signal circuit terminal G for a short to ground. If the circuit tests normal, replace the BCM.
  8. Install a 3A fused jumper wire between the signal circuit terminal F and ground. Verify the scan tool Driver Door Unlock Sw parameter is Active.
  9. 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.
  10. Install a 3A fused jumper wire between the signal circuit terminal G and ground. Verify the scan tool Driver Door Lock Sw parameter is Active
  11. 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.
  12. If all circuits test normal, test or replace the driver door lock switch.

Passenger/Cargo Door Lock Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the passenger and cargo door lock switches.
  2. Test for less than 1 ohm between the ground circuit terminal listed below and ground:
  3. • Passenger door lock switch terminal A
    • Rear cargo door lock switch terminal E
    If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Psgr Door Lock Sw parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the BCM.
    • Passenger door lock switch terminal F
    • Rear cargo door lock switch terminal A
  6. Verify the scan tool Psgr Door Unlock Sw parameter is Inactive.
  7. If not the specified value, test the signal circuit terminal listed below for a short to ground. If the circuit tests normal, replace the BCM.
    • Passenger door lock switch terminal G
    • Rear cargo door lock switch terminal D
  8. Install a 3A fused jumper wire between the signal circuit terminal listed below and ground:
  9. • Passenger door lock switch terminal F.
    • Rear cargo door lock switch terminal A.
  10. Verify the scan tool Psgr Door Lock Sw parameter is Active.
  11. 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.
  12. Install a 3A fused jumper wire between the signal circuit terminal listed below and ground:
  13. • Passenger door lock switch terminal G.
    • Rear cargo door lock switch terminal D.
  14. Verify the scan tool Psgr Door Unlock Sw parameter is Active.
  15. 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.
  16. Ignition OFF, connect the harness connector at the passenger door lock switch.
  17. Ignition ON, observe the Psgr Door Lock Sw and Psgr Door Unlock Sw parameters while using the passenger door lock switch. The parameters should change from Inactive to Active.
  18. If the values do not change, test or replace the passenger door lock switch.
  19. If all circuits test normal, test or replace the cargo door lock switch.

Door Lock Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the body fuse block.
  2. Test for less than 1 ohm between the ground circuit terminal 22 and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Connect a test lamp between the control circuit terminal 11 and B+
  5. Ignition ON, command the doors to UNLOCK by using the door lock switch. The test lamp should briefly illuminate when commanding the UNLOCK state.
  6. 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.
  7. Connect a test lamp between the control circuit terminal 18 and B+.
  8. Command the doors to UNLOCK by using the door lock switch. The test lamp should briefly illuminate when commanding the UNLOCK state.
  9. 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.
  10. Connect a test lamp between the control circuit terminal 5 and ground.
  11. Command the doors to LOCK by using the door lock switch. The test lamp should briefly illuminate when commanding the LOCK state.
  12. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    If the test lamp is always OFF, test the control circuit for a short to ground or and open/high resistance. If the circuit tests normal, replace the BCM.
  13. Connect a test lamp between the control circuit terminal 19 and ground.
  14. Command the doors to LOCK by using the door lock switch. The test lamp should briefly illuminate when commanding the LOCK state.
  15. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    If the test lamp is always OFF, test the control circuit for a short to ground or and open/high resistance. If the circuit tests normal, replace the BCM.
  16. Ignition OFF, connect the harness connector at the body fuse block and disconnect the harness connector at the appropriate door latch.
  17. Test for less than 1 ohm between the control circuit terminal A and ground.
  18. If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the body fuse block.
  19. Test for less than 1 ohm between the control circuit terminal B and ground.
  20. If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the body fuse block.
  21. Connect a test lamp between the control circuit terminal A and control circuit terminal B.
  22. Ignition ON, command the door latch to LOCK and UNLOCK by using the door lock switch. The test lamp should briefly illuminate when commanding the LOCK and UNLOCK states.
  23. If the test lamp is always OFF during either of the commands, test both control circuits for a short to ground. If the circuits test normal, replace the body fuse block.
  24. If all circuits test normal, test or replace the door latch.

Sliding Door Lock Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate door contact plate.
  2. Test for less than 1 ohm between the control circuit terminal B and ground.
  3. If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance.
  4. Test for less than 1 ohm between the control circuit terminal A and ground.
  5. If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance.
  6. Connect a test lamp between control circuit terminal B and control circuit terminal A.
  7. Ignition ON, command the doors to LOCK and UNLOCK by using the door lock switch. The test lamp should briefly illuminate when commanding the LOCK and UNLOCK states.
  8. If the test lamp remains OFF during either of the commands, test either control circuit for a short to ground. If the circuit tests normal, replace the body fuse block.
  9. Ignition OFF, connect the harness connector at the door contact plate. Close the sliding door and disconnect the harness connector at the door lock acturator.
  10. Test for less than 1 ohm between the control circuit terminal B and ground.
  11. If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the door contact plate.
  12. Test for less than 1 ohm between the control circuit terminal A and ground.
  13. If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the door contact plate.
  14. Connect a test lamp between control circuit terminal B and control circuit terminal A.
  15. Ignition ON, command the doors to LOCK and UNLOCK by using the door lock switch. The test lamp should briefly illuminate when commanding the LOCK and UNLOCK states.
  16. If the test lamp remains OFF during either of the commands, test both control circuits for a short to ground or an open/high resistance. If the circuits test normal, replace the door contact plate.
  17. If all circuits test normal, test or replace the door lock acturator.

Component Testing

Door Lock Switch Test

  1. Ignition OFF, disconnect the harness connector at the appropriate door lock switch.
  2. Test for infinite resistance between the signal terminals and the ground terminal listed below with the switch in the inactive position:
  3. • Driver door lock switch terminal F and A
    • Driver door lock switch terminal G and A
    • Passenger door lock switch terminal F and A
    • Passenger door lock switch terminal G and A
    • Rear cargo door lock switch terminal A and E
    • Rear cargo door lock switch terminal D and E
    If less than the specified value, replace the door lock switch.
  4. Test for less than 2 ohms between the signal terminal and the ground terminal listed below with the switch in the lock position:
  5. • Driver door lock switch terminal F and A
    • Passenger door lock switch terminal F and A
    • Rear cargo door lock switch terminal A and E
    If greater than the specified value, replace the door lock switch.
  6. Test for less than 2 ohms between the signal terminal and the ground terminal listed below with the switch in the unlock position:
  7. • Driver door lock switch terminal G and A
    • Passenger door lock switch terminal G and A
    • Rear cargo door lock switch terminal D and E
    If greater than the specified value, replace the door lock switch.

Door Lock Actuator Test

  1. Ignition OFF, disconnect the harness connector at the appropriate door latch.
  2. Install a 15A fused jumper wire between one of the control terminals and 12V. Momentarily install a jumper wire between the other control terminal and ground. Reverse the jumper wires at least two times, the door latch should perform the LOCK/ UNLOCK functions.
  3. If it does not perform as specified, replace the door latch

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Side Door Lock Replacement
    •  Rear Door Lock Replacement
    •  Body Wiring Harness Junction Block Replacement
    •  Door Lock Switch Replacement
    •  Sliding Door Jamb Contact Plate Replacement
    •  Control Module References for BCM replacement, setup, and programming