Low Beams

WARNING: This page is about a different car, the 2018 Lincoln MKC. However, it is still accessible from the selected car via links, so may be relevant.

The BCM monitors the headlamp switch position by sending voltage signals on multiple circuits to the headlamp switch. There is one circuit for each headlamp switch position. At any given time, one of the signal circuits is switched to ground to indicate the headlamp switch position.

The BCM turns the parking lamps and headlamps on when the ignition is in RUN and the BCM detects a fault from the headlamp switch or wiring. This is normal behavior of the BCM when a fault has been detected with the inputs from the headlamp switch.

The BJB supplies voltage to the ballasts on each headlamp assembly.

The BCM supplies a high current switched voltage to the headlamp assemblies to supply the necessary current to operate the lamps. The BCM provides a low current voltage signal to the headlamp assemblies to switch on the lamps.

Vehicles with High Intensity Discharge (HID) headlamps utilize a ballast, mounted to each headlamp assembly, to provide the necessary voltage to illuminate the High Intensity Discharge (HID) bulbs.

The BCM also provides an Field Effect Transistor (FET) protection of the exterior lamps switched voltage and low beam output circuits. When an excessive current draw is detected, the BCM disables the affected circuit driver.

Refer to: Module Controlled Functions - System Operation and Component Description .