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

Driver Door Module B+

U0199 00

U0199 00

--

--

Front Passenger Door Module B+

U0200 00

U0200 00

--

--

Driver Door Latch Control

1

1

1

--

Passenger Door Latch Control

2

2

2

--

Door Lock Relay Control

B3135 00

B3135 00

B3135 00

--

Door Unlock Relay Control

B3130 00

B3130 00

B3130 00

--

Rear Door Latch Control

3,4

3,4

3,4

--

Door Lock/Unlock Relay Ground

--

3,4

3,4

--

Driver Door Module Ground

--

U0199 00

1

--

Front Passenger Door Module Ground

--

U0200 00

2

--

1. Driver Door Latch Malfunction

2. Passenger Door Latch Malfunction

3. Rear Door Unlock Inoperative

4. Rear Door Lock Inoperative

Circuit/System Description

The driver and front passenger power door lock switches are integral components of the driver door module (DDM) and front passenger door module (PDM). The switches consist of 2 positions, lock and unlock, and are in the normally open state. When placed in either the lock or unlock positions, the switches provide a direct input to their respective door control module. When a power door lock switch is operated to the lock or unlock position, the associated door control module responds by sending a serial data message indicating a change in the switch's position. This serial data message is received by the opposite door control module as well as the body control module (BCM). The DDM and PDM respond to the lock/unlock request by activating their associated power door lock motors to the appropriate direction to lock or unlock the front doors. The BCM is responsible for controlling the left and right rear passenger door lock motors. The BCM, upon receipt of a lock or unlock serial data signal, will control either the rear door lock or unlock relay. When the appropriate door lock relay is energized, the rear power door lock motors will lock or unlock the rear doors.

Reference Information

Schematic Reference

Door Lock/Indicator Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Door Latch 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 the front doors to LOCK and UNLOCK by using the driver and passenger door lock switches. The front doors should perform the LOCK and UNLOCK functions from each switch.
  2. If a front door does not perform the LOCK or UNLOCK function, refer to Front Door Lock Malfunction.
  3. Command the rear doors to LOCK and UNLOCK with a scan tool. The rear doors should perform LOCK and UNLOCK functions.
  4. If a rear door does not LOCK or UNLOCK, refer to Rear Door Lock Malfunction.

Circuit/System Testing

Front Door Lock Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the appropriate door module.
  2. Test for less than 1 ohm between the ground circuit terminal 6 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 B+ circuit terminal 4 and ground.
  5. If the test lamp does not illuminate, test the B+ circuit for a short to ground or open/high resistance. If the circuit tests normal and the door module fuse is open, replace the door module.
  6. Ignition OFF, connect the X1 harness connector at the door module and disconnect the harness connector at the front door latch.
  7. Ignition ON, test for less than 5 ohms between the control circuit terminal listed below and ground:
  8. • Driver door latch control circuit terminal 2
    • Driver door latch control circuit terminal 3
    • Front passenger door latch control circuit terminal 5
    • Front passenger door latch control circuit terminal 6
    If greater than the specified range, test the control circuit for a short to voltage or an open/hign resistance. If the circuit tests normal, replace the door module.
  9. Connect a test lamp between control circuit terminals of the front door latch listed below:
  10. • Driver door latch control circuit terminal 2 and control circuit terminal 3
    • Front passenger door latch control circuit terminal 5 and control circuit terminal 6
  11. 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.
  12. If the test lamp is always OFF during either of the commands, test either control circuit for a short to ground. If the circuits test normal, replace the door module.
  13. If all circuits test normal, test or replace the front door latch.

Rear Door Lock Malfunction

  1. Ignition OFF, disconnect the UNLOCK relay.
  2. Test for less than 20 ohms between the ground circuit terminal 87A and ground.
  3. If greater than the specified range, test the ground circuit for a short to voltage or an open/high resistance.
  4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal listed below and ground:
  5. • B+ circuit terminal 86
    • B+ circuit terminal 87
    If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance
  6. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
  7. Command the doors to UNLOCK with a scan tool. The test lamp should briefly illuminate during the UNLOCK command.
  8. If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
    If the test lamp continuously illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
  9. Ignition OFF, connect the UNLOCK relay and disconnect the LCK relay.
  10. Test for less than 20 ohms between the ground circuit terminals listed below and ground:
  11. • Ground circuit terminal 85
    • Ground circuit terminal 87A
    If greater than the specified range, test the ground circuit for a short to voltage or an open/high resistance.
  12. Connect a test lamp between the ground circuit terminal 85 and the control circuit terminal 86.
  13. Command the doors to LOCK with a scan tool. The test lamp should briefly illuminate during the LOCK command.
  14. If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
    If the test lamp continuously illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  15. Ignition OFF, connect the LOCK relay and disconnect the harness connector at the appropriate rear door latch.
  16. Test for less than 20 ohms between the control circuit terminal listed below and ground:
  17. • LR door latch control circuit terminal 2
    • RR door latch control circuit terminal 5
    If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the UNLOCK relay.
  18. Test for less than 20 ohms between the control circuit terminal listed below and ground:
  19. • LR door latch control circuit terminal 3
    • RR door latch control circuit terminal 6
    If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the LCK relay.
  20. Connect a test lamp between the control circuit terminal listed below and ground:
  21. • LR door latch control circuit terminal 2
    • RR door latch control circuit terminal 5
  22. Command the doors to UNLOCK with a scan tool. The test lamp should briefly illuminate during the UNLOCK command.
  23. If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the UNLOCK relay.
    If the test lamp continuously illuminates, test the control circuit for a short to voltage. If the circuit tests normal, test or replace the UNLOCK relay.
  24. Connect a test lamp between the control circuit terminal listed below and ground:
  25. • LR door latch control circuit terminal 3
    • RR door latch control circuit terminal 6
  26. Command the doors to LOCK with a scan tool. The test lamp should briefly illuminate during the LOCK command.
  27. If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the LCK relay.
    If the test lamp continuously illuminates, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the LCK relay.
  28. If all circuits test normal, test or replace the rear door latch.

Component Testing

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. Test for less than 2 ohms obetween terminals 30 and 87A.
  7. If greater than the specified value, replace the relay.
  8. Install a 25A 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.
  9. If greater than the specified value, replace the relay.

Door Latch Test

  1. Ignition OFF, disconnect the harness connector at the appropriate door latch.
  2. Ignition ON, install a 15 amp fused jumper wire between the control terminal listed below and 12 volts:
  3. • Driver door latch control terminal 3
    • Passenger door latch control terminal 5
    • Left rear door latch control terminal 3
    • Right rear door latch control terminal 6
  4. Momentarily install a jumper wire between the control terminal listed below and ground. The door latch should perform the LOCK/ UNLOCK function:
  5. • Driver door latch control terminal 4
    • Passenger door latch control terminal 6
    • Left rear door latch control terminal 2
    • Right rear door latch control terminal 5
    If the function does not perform as specified, replace the door latch.
  6. Reverse the jumper wires; the door latch assembly should perform the UNLOCK/LOCK function.
  7. If the function does not perform as specified, replace the door latch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Front Side Door Latch Replacement
    •  Rear Side Door Latch Replacement
    •  Control Module References for BCM, DDM, or PDM replacement, setup, and programming