Principles of Operation
WARNING: This page is about a different car, the 2003 Mercury Sable and 2003 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
The headlamps are supplied power at all times from the battery junction box (BJB). Ground is supplied through the multifunction switch and the headlamp switch. The flash-to-pass feature has ground supplied through the multifunction switch.