Grand Cherokee 2WD V8-4.7L VIN J (2004)
Headlamp Switch: Description and Operation
Headlamp Switch
The headlamp switch is part of the left multi-function switch. A knob on the end of the multi-function switch control stalk controls all of the exterior
lighting switch functions. The exterior lighting switch is hard wired to the Body Control Module (BCM).
The exterior lighting switch cannot be adjusted or repaired and, if faulty or damaged, the entire left multi-function switch unit must be replaced.
The exterior lighting switch uses a hard wired five volt reference circuit from the BCM, resistor multiplexing and a hard wired switch output circuit to
provide the BCM with a zero to five volt signal that indicates the status of all of the exterior lighting switch settings. The BCM then uses control outputs
to energize the headlamp and park lamp relays that activate the exterior lighting circuits.
The BCM monitors the exterior lighting switch status, then sends the proper switch status messages to other modules over the Programmable
Communications Interface (PCI) data bus network. The exterior lighting switch status is also used by the BCM as an input for chime warning system
operation.
