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

Each door lock switch is wired to the body control module (BCM) through a separate door lock/unlock signal circuit. While these circuits are separated between the BCM and respective door lock switch, they are connected into a single circuit within the BCM. The BCM supplies voltage through the door lock/unlock signal circuits to each door lock switch. When either door lock switch is operated, this supply voltage is pulled to ground, providing the BCM with the required lock or unlock signal. In order for the BCM to distinguish between a lock and unlock signal, the lock switch contains two separate paths for this voltage to flow to the same body ground. When the switch is operated to the unlock position, the supply voltage flows to ground through a 1.5 K ohm resistor. When the switch is operated to the lock position, the supply voltage flows to ground through a different part of the switch circuit, which has no resistor. The BCM then interprets the flow of voltage as a lock or unlock request and powers the door lock actuators to the appropriate lock or unlock position.

The BCM powers the reversible door latch assemblies by providing battery positive voltage and ground to the appropriate lock and unlock control circuits of the door latch assemblies. The Lock control circuits of the driver and passenger door latch assemblies are all connected together; however, the Unlock control circuits are connected in a slightly different way. While the unlock control circuits for the passenger door latch assemblies are connected together, the door latch assembly has a separate unlock control circuit. The system is designed this way so that the keyless entry transmitter may be used to unlock only the driver door. Despite this difference, all of the lock actuators perform much the same way. When the door latch assemblies are not active, all actuator Lock and Unlock control circuits are at ground potential within the BCM. Transitioning of the lock actuators to the lock or unlocked position depends upon which control circuits receive voltage and which control circuits receive ground.

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 parameters while pressing both the door lock and door unlock switches. The reading should change between LOCK and UNLOCK.

⇒	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 the Passenger Doors Unlock with a scan tool. All passenger doors should unlock.

⇒	If one or more passenger doors 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 A 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 lock control circuit terminal 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 unlock control circuit terminal 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 lock control circuit terminal and unlock control circuit terminal.
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 Test

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

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

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

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

Door Latch

1. Install a 15-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 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.