Each door lock contains a door ajar switch. The door ajar switches are an integral part of each door lock and are not serviced separately. The body control module (BCM) supplies voltage to each door ajar switch. Ground for each ajar switch is provided by a ground circuit connected to a ground stake. When the doors are closed, the ajar switch contacts of each door are open. When a vehicle door is ajar, the ajar switch contacts for that door are closed and the BCM interprets the flow of voltage as a discrete input from the door ajar switch. The BCM then sends the request to illuminate the corresponding door ajar indicator, via the class 2 serial data circuit, to the DIC. The DIC illuminates the appropriate door ajar indicator.