Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

When a door lock switch is activated in the lock or unlock position the BCM will receive a voltage signal on either the door lock switch lock or unlock signal circuits.

The BCM, upon receipt of a lock switch lock or unlock signal, will switch the appropriate lock relay control circuits to battery positive voltage. This will energize the appropriate lock or unlock relays. The relay will supply voltage to the door lock actuator lock or unlock control circuits to one side of the lock actuator. Since the opposing side of the lock actuators are connected to ground through the other lock actuator control circuit and the normally closed contacts of the lock or unlock relay, the doors and liftgate will then lock or unlock appropriately.

Three relays are used to operate the locks. DRV DR UNLCK relay, PASS DR UNLOCK and DR LCK relay. This is done to isolate the driver door lock actuator so it can be unlocked by itself using the keyless entry transmitter.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

Scan Tool Reference

1. Ignition ON, observe the scan tool Lock Switch and Unlock Switch parameters while pressing both the door lock and door unlock switches. The reading should change between ON and OFF.

⇒	If the reading does not change, refer to Door Lock Switch Malfunction.

2. Command the Driver Door Unlock ON and OFF with a scan tool. The driver door should unlock.

⇒	If the driver door does not unlock, refer to Driver Door Unlock Relay Malfunction.

3. Command the Passenger Door Unlock ON and OFF with a scan tool. All of the passenger doors should unlock.

⇒	If one or more passenger door do not unlock, refer to Passenger Door Unlock Relay Malfunction.

4. Press the door lock switch. All of the vehicle doors should lock.

⇒	If one or more vehicle doors do not lock, refer to Door Lock Relay Malfunction.

Door Lock Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the applicable door lock switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A and ground.

⇒	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 B+ circuit terminal A for a short to ground.

3. Verify the scan tool Lock Switch and Unlock Switch parameters are OFF.

⇒	If not the specified value, test the appropriate signal circuit terminal for a short to voltage. If the circuit tests normal, replace the BCM.

4. Install a 3-amp fused jumper wire between the signal circuit terminal B and the B+ circuit terminal A. Verify the scan tool Lock Switch parameter is ON.

⇒	If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

5. Install a 3-amp fused jumper wire between the signal circuit terminal C and the B+ circuit terminal A. Verify the scan tool Unlock Switch parameter is ON.

⇒	If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

6. If all circuits test normal, test or replace the applicable door lock switch.

Driver Door Unlock Relay Malfunction

1. Ignition OFF, disconnect the DRV DR UNLCK relay.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the switch side ground circuit terminal and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition OFF, test for less than 1.0 ohm of resistance between the coil side ground circuit terminal and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

4. Ignition ON, verify that a test lamp does not illuminates between the switch side control circuit terminal and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

5. Verify that a test lamp illuminates between the switch side B+ circuit terminal and ground.

⇒	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 coil control circuit terminal and the coil side ground circuit terminal.
7. Command the Driver Door Unlock ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always OFF, 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 is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

8. Install the DRV DR UNLCK relay.
9. Disconnect the harness connector at the driver door latch.
10. Ignition OFF, test for less than 5.0 ohm of resistance between the ground circuit terminal 3 and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, test or replace the DR LCK relay.

11. Connect a test lamp between the control circuit terminal 2 and the ground circuit terminal 3.
12. Command the Driver Door Unlock ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, test or replace the DRV DR UNLCK relay.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the DRV DR UNLCK relay.

13. If all circuits test normal, test or replace the driver door latch.

Passenger Door Unlock Relay Malfunction

1. Ignition OFF, disconnect the PASS DR UNLOCK relay.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the switch side ground circuit terminal and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition OFF, test for less than 1.0 ohm of resistance between the coil side ground circuit terminal and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

4. Ignition ON, verify that a test lamp does not illuminates between the switch side control circuit terminal and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

5. Verify that a test lamp illuminates between the switch side B+ circuit terminal and ground.

⇒	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 coil control circuit terminal and the coil side ground circuit terminal.
7. Command the Passenger Door Unlock ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always OFF, 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 is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

8. Install the PASS DR UNLOCK relay.
9. Disconnect the harness connector at the applicable door latch.
10. Ignition OFF, test for less than 5.0 ohm of resistance between the ground circuit terminal 3 and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, test or replace the DR LCK relay.

11. Connect a test lamp between the control circuit terminal 2 and the ground circuit terminal 3.
12. Command the Passenger Door Unlock ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, test or replace the PASS DR UNLOCK relay.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the PASS DR UNLOCK relay.

13. If all circuits test normal, test or replace the applicable door latch.

Door Lock Relay Malfunction

1. Ignition OFF, disconnect the DR LCK relay.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the switch side ground circuit terminal and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition OFF, test for less than 1.0 ohm of resistance between the coil side ground circuit terminal and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

4. Ignition ON, verify that a test lamp does not illuminates between the switch side control circuit terminal and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

5. Verify that a test lamp illuminates between the switch side B+ circuit terminal and ground.

⇒	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 coil control circuit terminal and the coil side ground circuit terminal.
7. Press and release the door lock switch. The test lamp should turn ON and OFF when pressing and releasing the switch.

⇒	If the test lamp is always OFF, 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 is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

8. Install the DR LCK relay.
9. Disconnect the harness connector at the applicable door latch.
10. Ignition OFF, test for less than 5.0 ohm of resistance between the ground circuit terminal 2 and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance. If the circuit tests normal, test or replace the applicable lock relay.

11. Connect a test lamp between the control circuit terminal 3 and the ground circuit terminal 2.
12. Press and release the door lock switch. The test lamp should turn ON and OFF when pressing and releasing the switch.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, test or replace the DR LCK relay.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the DR LCK relay.

13. If all circuits test normal, test or replace the applicable door latch.

Door Lock Switch Test

1. Ignition OFF, disconnect the harness connector at the applicable door lock switch.
2. Test for infinite resistance between the signal terminals B and C and the B+ terminal A with the switch in the open position.

⇒	If less than infinite resistance, replace the applicable door lock switch.

3. Test for less than 2 ohms of resistance between the signal terminal B and the B+ terminal A with the switch in the lock position.

⇒	If greater than 2 ohms, replace the applicable door lock switch.

4. Test for less than 2 ohms of resistance between the signal terminal C and the B+ terminal A with the switch in the unlock position.

⇒	If greater than 2 ohms, replace the applicable door lock switch.

Door Lock Actuator Test

1. Install a 20-A fused jumper wire between the control terminal 3 and 12 volts. Install a jumper wire between the ground terminal 2 and ground.
2. Verify the actuator turns on & off.

⇒	If the function does not perform as specified, replace the applicable door latch.

Relay Test

1. Ignition OFF, disconnect the applicable relay.
2. Test for 60-200 ohms of resistance between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•	· 30 and 86

•	· 30 and 87

•	· 30 and 85

•	· 85 and 87

⇒	If less than infinite resistance, replace the relay.

4. Test for less than 2 ohms of resistance between terminals 30 and 87A.

⇒	If greater than 2 ohms, replace the relay.

5. Install a 3-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Measure for less than 2 ohms of resistance between terminals 30 and 87.

⇒	If greater than 2 ohms, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.