The body control module (BCM) monitors the voltage level of the key switch lock and unlock signal circuits. When the key is inserted into the driver door key cylinder and turned to the Unlock or Lock position, a switch within the driver door latch closes causing the voltage to drop within the appropriate key switch signal circuit. The BCM will detect the drop in voltage and will command all the doors to unlock or lock.

Schematic Reference

Interior Lights 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

Ignition ON, insert the key into the drivers door lock cylinder, turn the key to the LOCK position and then to the UNLOCK positon while observing the driver and passenger doors. All doors should perform the LOCK and UNLOCK functions.

1. Ignition OFF, disconnect the harness connector at the driver door latch.
2. Test for less than 1 ohm between the ground circuit terminal 8 and ground.

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

3. Ignition ON, test for greater than 9V between the signal circuit terminal 4 and ground.

⇒	If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

4. Verify the scan tool Door Key Cyl. Unlock Switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal 9 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 9 and ground, verify the scan tool Door Key Cyl. Unlock Switch parameter is Active.

⇒	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.

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

1. Ignition OFF, disconnect the harness connector at the driver door latch.
2. Test for infinite resistance between the signal terminal 4 and the ground terminal 8 with the switch in the open position.

⇒	If not the specified value, replace the driver door latch.

3. Test for infinite resistance between the signal terminal 9 and the ground terminal 8 with the switch in the open position.

⇒	If not the specified value, replace the driver door latch.

4. Test for less than 2 Ω between the signal terminal 4 and the ground terminal 8 with the switch in the Lock position.

⇒	If greater than the specified range, replace the driver door latch.

5. Test for less than 2 Ω between the signal terminal 9 and the ground terminal 8 with the switch in the Unlock position.

⇒	If greater than the specified range, replace the driver door latch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.