The body control module (BCM) provides battery positive voltage and ground to the appropriate lock and unlock control circuits of the door lock and unlock relays. The lock control circuits of the driver and passenger door latch assemblies share a common relay; however, the unlock control circuits have separate relays. The system is designed this way so that the keyless entry transmitter may be used to unlock only the driver door.

The BCM supplies and monitors a reference voltage to the door lock switch through the door lock switch lock/unlock signal circuit. The door lock switch also receives a constant ground source. If a door lock switch is placed in the lock position or unlock position, the BCM detects the voltage drop on the signal circuit.

The BCM, upon receipt of a lock switch lock signal, will switch the all lock relay control circuit to battery positive voltage. This will energize the lock relay. The relay will supply voltage to the door lock actuator lock 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 will then lock appropriately. The remaining unlock relays receive voltage from the I/P fuse block, the BCM upon receipt of a unlock signal or driver door unlock signal will switch the appropriate unlock relay to ground. This will energize the appropriate unlock relay. The relay will supply voltage to the appropriate door unlock control circuits to one side of the appropriate lock actuator. Since the opposing side of the lock actuators are connected to ground through the other lock actuator control circuits and the normally closed contact of the lock relay, the doors will then unlock appropriately.

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

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool Rear Doors Lock Cmd and Rear Doors Unlock Cmd parameters while using the driver door lock switch. The parameter should change between On and Off when changing between the commanded states.

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

2. Command the door latches to LOCK and UNLOCK by using the driver door lock switch, the doors should perform the LOCK and UNLOCK functions.

⇒	If a door latch does not LOCK or UNLOCK, refer to Door Lock Malfunction.

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 2 and ground.

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

3. Ignition ON, verify the scan tool Rear Doors Lock Cmd parameter is Off.

⇒	If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the BCM.

4. Verify the scan tool Rear Doors Unlock Cmd parameter is Off.

⇒	If not the specified value, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the BCM.

5. Install a 3A fused jumper wire between the signal circuit terminal 1 and ground. Verify the scan tool Rear Doors Lock Cmd parameter is On.

⇒	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.

6. Install a 3A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Rear Doors Unlock Cmd parameter is On.

⇒	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.

7. If all circuits test normal, test or replace the driver door lock switch.

Door Lock Malfunction

1. Ignition OFF, disconnect the X1 harness connector at the I/P fuse block.
2. Test for less than 1 ohm between the ground circuit terminal 57 and ground.

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

3. Connect a test lamp between the control circuit terminal 56 and ground.
4. Ignition ON, command the Lock Rear Doors 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, replace the BCM

⇒	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

5. Connect a test lamp between the control circuit terminal 54 and B+.
6. Command the doors to UNLOCK by using the driver door lock switch. The test lamp should illuminate when commanding the UNLOCK state.

⇒	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 and open/high resistance. If the circuit tests normal, replace the BCM

7. Connect a test lamp between the control circuit terminal 58 and B+.
8. Command the doors to UNLOCK by using the driver door lock switch. The test lamp should illuminate when commanding the UNLOCK state.

⇒	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 and open/high resistance. If the circuit tests normal, replace the BCM.

9. Ignition OFF, connect the X1 harness connector at the I/P fuse block and disconnect the harness connector at the appropriate door latch.
10. Test for less than 1 ohm between the control circuit terminal and ground of the door latch listed below:

•	Driver door latch terminal 2

•	Driver door latch terminal 3

•	LR door latch terminal 2

•	LR door latch terminal 3

•	RR door latch terminal 5

•	RR door latch terminal 6

•	Passenger door latch terminal 5

•	Passenger door latch terminal 6

⇒	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 I/P fuse block.

11. Connect a test lamp between control circuit terminals of the door latch listed below:

•	Driver door latch terminal 2 and terminal 3

•	LR door latch terminal 2 and terminal 3

•	RR door latch terminal 5 and terminal 6

•	Passenger door latch terminal 5 and terminal 6

12. Ignition ON, command the door latch to LOCK and UNLOCK by using the driver door lock switch. The test lamp should illuminate when commanding the LOCK and UNLOCK states.

⇒	If the test lamp does not illuminate during either of the commands, test either control circuit for a short to ground. If the circuits test normal, replace the I/P fuse block.

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

Door Lock Switch

1. Ignition OFF, disconnect the harness connector at the driver door lock switch.
2. Test for infinite resistance between the signal terminals 3 and 1 and the ground terminal 2 with the switch in the open position.

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

3. Test for less than 2 ohms between the signal terminal 1 and the ground terminal 2 with the switch in the LOCK position.

⇒	If greater than the specified range, replace the driver door lock switch.

4. Test for less than 2 ohms between the signal terminal 3 and the ground terminal 2 with the switch in the UNLOCK position.

⇒	If greater than the specified range, replace the driver door lock switch.

Door Latch Assembly

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.

⇒	If it does not perform as specified, replace the door latch

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.