Low Beams

WARNING: This page is about a different car, the 2018 Lincoln Navigator. 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.

When the ignition is in ON, the BCM supplies voltage to the LED control module attached to each headlamp assembly through the low beam headlamp circuit. This LED control module is used to control the low beam LED.

When the BCM receives a message requesting the headlamps on, it sends a low beam message over the HS-CAN1 to the HCM. The HCM sends the low beam message over the LIN circuit to the LED control module attached to each headlamp assembly to illuminate the low beam LED.

The BCM also provides Field Effect Transistor (FET) protection of the 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 .