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

The DR LCK fuse supplies battery positive voltage to the body control module (BCM) for the door lock system. 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, the reference voltage is taken directly to ground and the BCM senses 0.0 volts on the signal circuit. If a door lock switch is placed in the unlock position, the reference voltage is taken to ground through a 1.5k ohm resistor that is internal to the door lock switches and senses approximately 2.9 volts on the signal circuit. This is how the BCM determines what portion of the door lock switch was activated.

The BCM, upon receipt of a door lock switch lock or unlock signal, will switch the appropriate door lock actuator control circuits to battery positive voltage. The opposing side of the door lock actuators are connected to ground internally within the BCM through the other door lock actuator control circuit and the doors will lock or unlock appropriately.

Vehicles without keyless entry have two internal drivers in the BCM to control the door lock actuators. All door lock and all door unlock. Vehicles equipped with keyless entry have three internal drivers in the BCM. Driver door unlock, passenger door unlock and all door lock. This is done to isolate the driver door lock actuator so it can be unlocked by itself using the keyless entry transmitter.

Schematic Reference

Door Lock/Indicator Schematics

Connector End View Reference

Power Door Systems Connector End Views

Description and Operation

Power Door Locks Description and Operation

Electrical Information Reference

Scan Tool Reference

1. Ignition ON, observe the scan tool Door Lock Switch parameter while using the appropriate door lock switch. The parameter should change from Idle to Lock and Unlock.

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

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

⇒	If one or more doors do not LOCK or UNLOCK, refer to Door Lock 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 E 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 Switch parameter is Idle.

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

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

⇒	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.

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

Door Lock Malfunction

1. Ignition OFF, disconnect the C4 harness connector at the BCM.
2. Test for less than 1 ohm between the ground circuit terminal E12 and ground.

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

3. Connect the C4 harness connector and disconnect the harness connector at the appropriate door latch.
4. Test for less than 1 ohm 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 circuit tests normal, replace the BCM.

5. Test for less than 1 ohm between the control circuit terminal 3 and ground.

⇒	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, replace the BCM.

6. Connect a test lamp between control circuit terminal 2 and control circuit terminal 3.
7. Ignition ON, command the door latch to LOCK and UNLOCK with a scan tool. The test lamp should briefly illuminate when commanding the LOCK and UNLOCK states.

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

8. 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 terminal A and the ground terminal E with the switch in the idle position.

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

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

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

4. Test for 1.4K-1.6K ohms of resistance between the signal terminal A and the ground terminal E with the switch in the unlock position.

⇒	If not within the specified range, replace the door lock switch.

Door Latch

1. Ignition OFF, disconnect the harness connector at the appropriate door latch.
2. Install a 15-amp fused jumper wire between the control terminal 2 and 12 volts. Momentarily install a jumper wire between the control terminal 3 and ground. The door latch should perform the LOCK/ UNLOCK function

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

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

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.