GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 Envoy - 2WD 🢒 Body Systems 🢒 Vehicle Access 🢒 Power Door Locks Inoperative - Front

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 Switch B+

1

1

--

--

Door Lock Relay B+

3,4

3,4

--

--

Door Unlock Relay B+

3,4

3,4

--

--

Passenger Door Switch B+

2

2

--

--

Driver Door Latch Control

1

1

1

--

Passenger Door Latch Control

2

2

2

--

Door Lock Relay Control

B3808

B3808

3,4

--

Door Unlock Relay Control

B3809

B3809

3,4

--

Liftgate Latch Control

5

5

5

--

Rear Door Latch Control

3,4

3,4

3,4

--

Door Lock Relay Ground

--

3,4

3,4

--

Door Unlock Relay Ground

--

3,4

3,4

--

1. Driver Door Latch Malfunction

2. Passenger Door Latch Malfunction

3. Rear Door Unlock Inoperative

4. Rear Door Lock Inoperative

5. Liftgate Latch Inoperative

Circuit/System Description

The driver and front passenger power door lock switches are integral components of the driver door switch (DDS) and passenger door switch (PDS). 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 there 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) and the liftgate module (LGM). The DDS, PDS and LGM respond to the lock/unlock request by activating there 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 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

Ignition ON, command the front doors to LOCK and UNLOCK by using the driver and passenger door lock switches, the doors should perform LOCK and UNLOCK function from each switch.

⇒If the driver door does not LOCK or UNLOCK, refer to Driver Door Lock Malfunction.
⇒If the passenger door does not LOCK or UNLOCK, refer to Passenger Door Lock Malfunction

Circuit/System Testing

Driver Door Lock Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the DDS.
  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.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal D and ground.
    4. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, connect the X1 harness connector and disconnect the X2 harness connector at the DDS.
  5. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal B5 and ground.
    6. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  6. Ignition OFF, connect the X2 harness connector at the DDS and disconnect the harness connector at the driver door latch.
  7. Test for less than 2 ohms between the control circuit terminal A and ground
    8. ⇒If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the DDS.
  8. Test for less than 2 ohms between the control circuit terminal B and ground.
    9. ⇒If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the DDS.
  9. Ignition ON, connect a test lamp between the control circuit terminal A and control circuit terminal B.
  10. Command the door to LOCK and UNLOCK by using the driver door lock switch. The test lamp should briefly illuminate when commanding the LOCK and UNLOCK states.
    11. ⇒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 DDS.
  11. If all circuits test normal, test or replace the driver door latch.

Passenger Door Lock Malfunction

  1. Ignition OFF, disconnect the X1 harness connector at the PDS.
  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.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal D and ground.
    4. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, connect the X1 harness connector and disconnect the X2 harness connector at the PDS.
  5. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal B5 and ground.
    6. ⇒If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  6. Ignition OFF, connect the X2 harness connector at the PDS and disconnect the harness connector at the passenger door latch.
  7. Test for less than 2 ohms between the control circuit terminal A and ground.
    8. ⇒If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the PDS.
  8. Test for less than 2 ohms between the control circuit terminal B and ground.
    9. ⇒If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the PDS.
  9. Ignition ON, connect a test lamp between the control circuit terminal A and control circuit terminal B.
  10. Command the door to LOCK and UNLOCK by using the passenger door lock switch. The test lamp should briefly illuminate when commanding the LOCK and UNLOCK states.
    11. ⇒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 PDS.
  11. If all circuits test normal, test or replace the passenger door latch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Side Door Latch Replacement
    •  Control Module References for DDS or PDS replacement, programming, and setup.