Principles of Operation

WARNING: This page is about a different car, the 2014 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

The Steering Column Control Module (SCCM) 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. The SCCM sends a message to the Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN), indicating the headlamp switch position.

When the BCM receives a network message from the SCCM that the headlamp switch is in the PARKING LAMPS ON position, the BCM provides voltage to the parking lamps.

If the SCCM does not detect any active inputs from the headlamp switch for 5 seconds, or if the SCCM detects multiple headlamp switch input circuits are active, the SCCM sends a message to the BCM to indicate the fault. The BCM then turns the parking lamps and headlamps on and keeps them on until the battery saver feature times out.

Refer to EXTERIOR LIGHTING in the Description and Operation portion of this article for information regarding the battery saver feature.

If either situation occurs, the SCCM and the BCM cannot be ruled immediately as being at fault. This is normal behavior of the SCCM and the BCM when a fault has been detected with the inputs from the headlamp switch.