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

BCM B+

1

1

--

--

Driver Door Lock Switch Unlock Signal

2

2

2

--

Driver Door Lock Switch Lock Signal

2

2

2

--

Passenger Door Lock Switch Unlock Signal

2

2

2

--

Passenger Door Lock Switch Lock Signal

2

2

2

--

Driver Door Lock Actuator Unlock Control

1

1

1

--

Door Lock Actuator Unlock Control

1

1

1

--

Door Lock Actuator Lock Control

1

1

1

--

Door Lock Switch Ground

--

2

2

--

BCM Ground

--

1

1

--

1. Door Lock Malfunction

2. Door Lock Switch Malfunction

Circuit/System Description

When the body control module (BCM) detects a transition of either of the door lock switches to the LOCK position, it switches the door lock actuator lock control circuit to voltage. Since the door lock actuator lock control circuit is at ground potential within the BCM, the door lock actuators transitions to the LOCK position and when the BCM detects a transition of either of the door lock switches to the UNLOCK position, it switches the door lock actuator unlock control circuit to voltage. Since the door lock actuator unlock control circuit is at ground potential within the BCM, the door lock actuators transitions to the UNLOCK position.

The driver door lock actuator unlock control circuit is a dedicated control circuit used only for the driver door lock actuator motor. This is done so that the driver door may be unlocked by itself using a keyless entry transmitter or an automatic door unlock function, if programmed.

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, command all doors LOCK and UNLOCK by using the driver door lock switch and the passenger door lock switch. All doors should perform the LOCK and UNLOCK functions from each switch.
  2. If the doors do not LOCK or UNLOCK while using the passenger door lock switch, refer to Passenger Door Lock Switch Malfunction.
    If the doors do not LOCK or UNLOCK while using the driver door lock switch, refer to Driver Door Lock Switch Malfunction.
  3. Command the Lock All Doors and Unlock All Doors with a scan tool, all doors should perform the LOCK and UNLOCK functions
  4. If the driver door does not LOCK or UNLOCK, refer to Driver Door Lock Malfunction.
    If one or all doors do not LOCK or UNLOCK, refer to Door Lock Malfunction.

Circuit/System Testing

Passenger Door Lock Switch Malfunction

  1. Ignition OFF, disconnect the harness connector at the front passenger door lock switch.
  2. Test for less than 1 ohm between the ground circuit terminal B 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 RF Door Lock Switch parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM.
  6. Verify the scan tool RF Door Unlock Switch parameter is Inactive.
  7. If not the specified value, test the signal circuit terminal E 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 D and ground. Verify the scan tool RF Door Lock Switch 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 E and ground. Verify the scan tool RF Door Unlock Switch 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 passenger door lock switch.

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 B and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for greater than 9 volts between the signal circuit terminal D and ground.
  5. If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.
  6. Test for greater than 9 volts between the signal circuit terminal E and ground.
  7. If less than the specified range, test the signal circuit 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 D and ground. Verify the doors perform the LOCK function.
  9. If the doors do not perform the LOCK function, 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 E and ground. Verify the doors perform the UNLOCK function.
  11. If the doors do not perform the UNLOCK function, 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.

Driver Door Lock Malfunction

  1. Ignition OFF, disconnect the harness connector at the driver door lock.
  2. Ignition ON, connect a test lamp between control circuit terminal 3 and control circuit terminal 2.
  3. Command the driver door to LOCK and UNLOCK using a scan tool. The test lamp should illuminate when changing between the commanded states.
  4. If the test lamp remains OFF during either of the commands, test either control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the BCM.
    If the test lamp is always ON, test either control circuit for a short to voltage. If the circuits test normal, replace the BCM.
  5. If all circuits test normal, test or replace the driver door lock.

Door Lock Malfunction

  1. Ignition OFF, disconnect the X2 harness connector at the BCM.
  2. Test for less than 1 ohm between the ground circuit terminal 50 and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 49 and ground.
  5. If the test lamp does not illuminate, test the B+ circuit for a short to ground or open/high resistance.
  6. Ignition OFF, connect the X2 harness connector at the BCM and disconnect the harness connector at the appropriate passenger door lock.
  7. Ignition ON, connect a test lamp between the control circuit terminals listed below.
  8. • Front passenger door lock terminals 5 and 6
    • LR passenger door lock terminals 2 and 3
    • RR passenger door lock terminals 5 and 6
  9. Command the Lock All Doors and Unlock All Doors with a scan tool. The test lamp briefly illuminate while commanding the LOCK and UNLOCK states.
  10. If the test lamp remains OFF during either of the commands, test either control circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the BCM.
    If the test lamp is always ON, test either control circuit for a short to voltage. If the circuits test normal, replace the BCM.
  11. If all circuits test normal, test or replace the passenger door lock.

Component Testing

Door Lock Switch

  1. Ignition OFF, disconnect the harness connector at the appropriate door lock switch.
  2. Test for infinite resistance between the signal terminal E and D and the ground terminal B with the switch in the open position.
  3. If not the specified value, replace the door lock switch.
  4. Test for less than 2 ohms between the signal terminal E and the ground terminal B with the switch in the UNLOCK position.
  5. If greater or less than the specified range, replace the door lock switch.
  6. Test for less than 2 ohms between the signal terminal D and the ground terminal B with the switch in the LOCK position.
  7. If greater than the specified range, replace the door lock switch.

Door Lock

  1. Ignition OFF, disconnect the harness connector at the appropriate door lock.
  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 lock should perform the LOCK/ UNLOCK functions.
  3. If it does not perform as specified, replace the door lock.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Rear Door Lock Replacement
    •  Door Lock Switch Replacement
    •  Front Side Door Lock Replacement
    •  Control Module References for BCM replacement, setup, and programming