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Home >> Mercury >> 2008 >> Milan Base, 3.0 1, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 721 (Exterior Lighting System) >> Diagnostic Tests >> Autolamps >> Pinpoint Tests >> Pinpoint Test F: The Autolamps Are Inoperative >> Normal Operation

Normal Operation

WARNING: This page is about a different car, the 2007 Lincoln Mark LT and 2007 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.

With the headlamp switch turned to the AUTOLAMP position, a battery voltage signal is sent to the vehicle security module (VSM) through circuit 220 (VT/OG). The VSM then determines the amount of ambient light based on the input received from the light sensor. The input signal from the light sensor to the VSM is received through circuit 218 (WH/VT). When the ambient level has reached a point (determined by the internal programming of the VSM), 2 internal relays are energized to supply voltage to the exterior lamps. Circuit 196 (DB/OG) supplies voltage to the internal headlamp relay, which then supplies voltage to circuit 15 (RD/YE) when energized. Circuit 195 (TN/WH) supplies voltage to an internal parking lamp relay, which then supplies voltage to circuit 14 (BN) when energized.

DTC B1793 - sets when the VSM detects a short to ground on the autolamp sensor input circuit.

Possible Causes

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