Headlamp Switch - Operation

OPERATION

The headlamp switch (also known as the Rotary Light Switch/RLS or light switch module) receives battery voltage at all times. The switch receives a path to ground at all times through the vehicle wire harness. The only output from the switch is a voltage signal that it provides to the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM). Each switch position selects a different tap on a series resistor within the switch to provide a different voltage signal to the BCM and the BCM controls the exterior lighting features accordingly.

The headlamp switch as well as the hard wired inputs and outputs of the switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the electronic controls and communication that provide some features of the exterior lighting system. Proper diagnosis of the BCM, the CAN data bus and the electronic communication related to exterior lighting system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.