The BCM PWR fuse supplies battery positive voltage to the 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 resister 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

Description and Operation

Power Door Locks 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 Door Lock Malfunction.

3. Command All Doors Lock ON and OFF with a scan tool. All of the passenger doors should lock.

⇒	If one or more passenger door do not unlock, refer to Door Lock 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 Malfunction

Door Lock Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate Door Lock Switch.
2. Ignition OFF, test for less than 1.0 ohm for resistance 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 Door Lock Switch is Idle.

⇒	If not the specified value, test the signal circuit terminal 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 and ground. Verify the scan tool Door Lock Switch is Lock or Unlock.

⇒	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.

5. If all circuits test normal, test or replace the appropriate Door Lock switch.

Door Lock Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate Door Latch.
2. Ignition OFF, test for less than 1.0 ohm of resistance 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 circuits test normal, replace the BCM.

3. Ignition OFF, test for less than 1.0 ohm of resistance 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 circuits test normal, replace the BCM.

4. Connect a test lamp between control circuit terminal 2 and control circuit terminal 3.
5. Command the Door Latch to LOCK and UNLOCK with a scan tool. The test lamp should turn ON when commanding the LOCK and UNLOCK states.

⇒	If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the BCM.

6. If all circuits test normal, test or replace the appropriate Door Latch.

Door Lock Switch

1. Ignition OFF, disconnect the harness connector at the appropriate Door Lock switch.
2. Test for infinite resistance between the signal terminal 1 and the ground circuit terminal 2 with the switch in the open position.

⇒	If not the specified value, replace the appropriate Door Lock switch.

3. Test for 1.4k-1.6k ohms between the signal terminal 1 and the ground circuit terminal 2 with the switch in the Unlock position.

⇒	If greater or less than the specified range, replace the appropriate Door Lock Switch.

4. Test for less than 2.0 ohms between the signal terminal 1 and the ground circuit terminal 2 with the switch in the Lock position.

Door Latch

1. 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 appropriate Door Latch should perform the LOCK/ UNLOCK function.

⇒	If the function does not perform as specified, replace the appropriate Door Latch.

2. Reverse the jumper wires; the appropriate Door Latch should perform the LOCK/UNLOCK function.
3. If the function does not perform as specified, replace the appropriate Door Latch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.