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 reference voltage is taken directly to ground and the BCM detects 0.0 volts 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 LCK 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 underhood 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 Driver Door Lock Sw, Psgr Door Lock Sw, Driver Door Unlock Sw. and Psgr Door Unlock Sw. parameters while using the appropriate door lock switch. The parameter should change between Inactive and Active.

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

2. Command the driver door and passenger door lock actuators to LOCK and UNLOCK with the scan tool, the doors should LOCK and UNLOCK.

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

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

⇒	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 appropriate door lock switch.
2. Test for less than 1 ohm between the ground circuit terminal B and ground.

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

3. Ignition ON, verify the scan tool Door Lock Sw. parameter is Inactive.

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

4. Verify the scan tool Door Unlock Sw. parameter is Inactive.

⇒	If not the specified parameter, test the signal circuit terminal D 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 D and ground. Verify the scan tool Door Unlock Sw. parameter is Active.

⇒	If not the specified parameter, 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 E and ground. Verify the scan tool Door Lock Sw. parameter is Active.

⇒	If not the specified parameter, 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 door lock switch.

Driver Door Unlock Relay Malfunction

1. Ignition OFF, disconnect the LT/UNLCK relay.
2. Test for less than 1 ohm between the ground circuit terminal 87A and ground.

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

3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 30 and ground.

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

4. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

6. Connect a test lamp between the control circuit terminal 85 and the B+ circuit terminal 86.
7. Command the driver door to UNLOCK with a scan tool. The test lamp should briefly illuminate when commanding the UNLOCK state.

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

8. Ignition OFF, connect the LT/UNLCK relay. Disconnect the harness connector at the driver door latch.
9. Ignition OFF, test for less than 5 ohms between the control circuit terminal 2 and ground.

⇒	If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuits test normal, replace the LT/UNLCK relay.

10. Connect a test lamp between control circuit terminal 2 and control circuit terminal 3.
11. Ignition ON, command the driver door latch to UNLOCK with a scan tool. The test lamp should briefly illuminate when commanding the UNLOCK state.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground. If the circuit tests normal, test or replace the LT/UNLCK relay.

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

Door Unlock Relay Malfunction

1. Ignition OFF, disconnect the UNLCK relay.
2. Test for less than 1 ohm between the ground circuit terminal 87A and ground.

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

3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 30 and ground.

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

4. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

6. Connect a test lamp between the control circuit terminal 85 and the B+ circuit terminal 86.
7. Command the rear doors to UNLOCK with a scan tool. The test lamp should briefly illuminate when commanding the UNLOCK state.

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

8. Ignition OFF, connect the UNLCK relay. Disconnect the harness connector at the appropriate door latch.
9. Ignition OFF, test for less than 5 ohms between the control circuit terminal of the door lock listed below and ground:

•	Driver door lock circuit terminal 2.

•	Left rear door lock circuit terminal 2

•	Front passenger door lock circuit terminal 5.

•	Right rear door lock 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 circuits test normal, replace the UNLCK relay.

10. Ignition ON, connect a test lamp between the control circuit terminals of the door lock listed below:

•	Driver door lock circuit terminals 2 and 3.

•	Left rear door lock circuit terminals 2 and 3

•	Front passenger door lock circuit terminals 5 and 6.

•	Right rear door lock circuit terminals 5 and 6

11. Ignition ON, command the door latch to UNLOCK with a scan tool. The test lamp should briefly illuminate when commanding the UNLOCK state.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground. If the circuit tests normal, test or replace the UNLCK relay.

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

Door Lock Relay Malfunction

1. Ignition OFF, disconnect the LCK relay.
2. Test for less than 1 ohm between the ground circuit terminal 87A and ground.

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

3. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 30 and ground.

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

4. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

6. Connect a test lamp between the control circuit terminal 85 and the ground circuit terminal 86.
7. Command the rear doors LOCK with a scan tool. The test lamp should briefly illuminate when commanding the LOCK state.

⇒	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. Ignition OFF, connect the LCK relay. Disconnect the harness connector at the appropriate door latch.
9. Test for less than 5 ohms between the control circuit terminal of the door lock listed below and ground:

•	Driver door lock circuit terminal 3.

•	Left rear door lock circuit terminal 3

•	Front passenger door lock circuit terminal 6.

•	Right rear door lock 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 circuits test normal, replace the LCK relay.

10. Ignition ON, connect a test lamp between the control circuit terminals of the door lock listed below:

•	Driver door lock circuit terminals 2 and 3.

•	Left rear door lock circuit terminals 2 and 3

•	Front passenger door lock circuit terminals 5 and 6.

•	Right rear door lock circuit terminals 5 and 6

11. Ignition ON, command the door latch to LOCK with a scan tool. The test lamp should briefly illuminate when commanding the LOCK state.

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

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

Door Lock Switch Test

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

⇒	If less than the specified value, replace the door lock switch.

3. Test for less than 2 ohms between the signal terminal E and the ground terminal B with the switch in the lock position.

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

4. Test for less than 2 ohms between the signal terminal D and the ground terminal B with the switch in the unlock position.

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

Door Latch Assembly

1. Ignition OFF, disconnect the harness connector at the appropriate door latch assembly.
2. Install a 25-amp fused jumper wire between the lock control terminal and 12 volts. Momentarily install a jumper wire between the unlock control terminal and ground. The door lock should perform the LOCK/ UNLOCK function.

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

3. Reverse the jumper wires; the appropriate door lock should perform the UNLOCK/LOCK function.

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

Relay Test

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

⇒	If 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 the specified value, replace the relay.

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

⇒	If greater than the specified range, replace the relay.

5. Install a 3-amp fused jumper wire between the 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.

⇒	If greater than specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.