Test A: One Door Switch Lock Function Inoperative

1. Turn ignition switch to LOCK position. Disconnect inoperative door lock switch harness connector. Connect DVOM between driver-side door lock switch connector terminals "C" (Red/Black wire) and "F" (Black wire) or passenger-side door lock switch connector terminals "B" (Red/Black wire) and "F" (Black wire). See Fig 1 . Resistance should be infinite. Press LOCK on affected door lock switch. Resistance should be less than 2 ohms. If resistance readings are as specified, go to next step. If resistance readings are not as specified, go to step  3 .
2. Repair poor connection or open in Red/Black wire between BCM and affected door lock switch. After repairs, go to step  4 .
3. Replace affected door lock switch. After replacing switch, go to next step.
4. Turn ignition switch to LOCK position. Reinstall connectors or components that were disconnected. Recheck system operation.

Fig 1: Identifying Power Door Lock Switch Terminals

Courtesy of GENERAL MOTORS CORP.