Normal Operation

WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

The lighting control module (LCM) sends voltage reference signals to the headlamp switch through circuits 220 (VT/OG) (autolamps position), 1400 (TN/WH) (off position), 1032 (WH/BK) (park position) and 1033 (RD/YE) (headlamp position). The headlamp switch routes the signal to ground through circuit 57 (BK) for any given headlamp switch position. If the LCM detects a fault with the headlamp switch input, the LCM defaults the exterior lamps on.

When a request for the autolamps is detected by the LCM, the LCM monitors the state of circuit 218 (WH/VT). When a low ambient light condition is present, the signal circuit is high, and the LCM supplies voltage to the exterior lamps. When a high ambient light condition is present, the light sensor pulls the voltage signal low, and the LCM deactivates the voltage to the exterior lamps. The light sensor is provided ground through circuit 676 (PK/OG).

The LCM also sends a voltage reference signal to the windshield wiper motor through circuit 28 (BK/PK). When the wiper motor is on, the signal is routed to ground.

DTC B1449 (Wiper Park Sense Circuit Short to Ground) - sets when the LCM detects a short to ground on the wipers on input circuit.
DTC B1472 (Lamp Headlamp Input Circuit Short to Ground) - sets when the LCM detects a short to ground on the headlamps on input circuit.
DTC B1696 (Autolamp On Circuit Short to Ground) - sets when the LCM detects a short to ground on the autolamps lamps on input circuit.

This pinpoint test is intended to diagnose the following:

Wiring, terminals or connectors
Light sensor
Headlamp switch
Windshield wiper motor
LCM