The key cylinder switch contains a signal circuit and a low reference circuit. When the door key is turned to unlock, the switch contacts, which are normally open, close and the driver door module (DDM) detects a switched ground. The DDM sends a message via a serial data message to the passenger door module (PDM), and body control module (BCM) to lock or unlock their respective doors.

Schematic Reference

Door Lock/Indicator 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

1. Ignition ON, observe the function of the door locks while performing the LOCK and UNLOCK command using the door lock switch, all doors should perform the LOCK and UNLOCK functions.

⇒	If any door fails to LOCK or UNLOCK, refer to Power Door Locks Inoperative .

2. Observe the scan tool Key Cyl Unlock Switch parameters while the turning and holding the key in the driver door lock cylinder to the unlock position, the parameter should change from Idle to Unlock.

1. Ignition OFF, disconnect the harness connector at the driver door lock switch.
2. Ignition ON, verify that a test lamp illuminates between the low reference circuit terminal B and B+.

⇒	If the test lamp does not illuminate, test the low reference circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Door Key Cyl. Unlock Switch parameter is Idle.

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

4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Door Key Cyl. Unlock Switch parameter is 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 DDM.

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

1. Ignition OFF, disconnect the harness connector at the driver door lock key cylinder switch.
2. Test for infinite resistance between the signal terminal A and the low reference terminal B with the switch in the Idle position.

⇒	If not the specified value, replace the driver door lock key cylinder switch.

3. Test for less than 2 ohms between the signal terminal A and the low reference terminal B with the switch in the unlock position.

⇒	If greater than the specified range, replace the driver door lock key cylinder switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.