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 common door lock signal circuit. The BCM supplies voltage through the door lock 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 body ground. When the switch is operated to the lock position, the supply voltage flows to ground through a 470 ohm resistor. When the switch is operated to the unlock 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 body control module (BCM) powers the reversible door latch assemblies by providing battery positive voltage and ground to the appropriate lock and unlock control circuits of the 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 lock actuators are connected together, the driver 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 lock actuators are not active, all actuator Lock and Unlock control circuits are at ground potential within the BCM. Transitioning of the latch assemblies to the lock or unlocked position depends upon which control circuits receive voltage and which control circuits receive ground.

Battery voltage must be between 9-16 volts.

B3270

The BCM detects a short to ground through 470 ohms of resistance in the door lock switch signal circuit for greater than 60 seconds.

B3272

The BCM detects a short to ground in the door lock switch signal circuit for greater than 60 seconds.

The conditions above must be present for more than 60 seconds

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

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 ON and OFF.

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 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 Unlock Switch is Inactive.

⇒	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 E 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.