Section 20 (Lamps/Lighting - Exterior (Service Information)): Operation: Headlamps

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

The headlamp system includes the IPC, the Steering Column Control Module (SCCM), the Body Control Module (BCM), the headlamp switch and the multi-function switch on the steering column. The headlamp bulbs have a path to ground at all times through their connection to the FEM wire harness. The FEM harness has takeouts with eyelet terminals that are secured to the front end sheet metal within the engine compartment. The BCM will store a Diagnostic Trouble Code (DTC) for any shorts or opens in the headlamp circuits.

The BCM monitors a hard wired multiplex input to determine the status of the headlamp switch. The BCM also monitors electronic headlamp beam select switch status messages received from the SCCM over the CAN data bus. The BCM responds to these inputs by providing a pulse width modulated voltage output to the headlamp bulbs through high side drivers on the right and left headlamp feed circuits to illuminate the headlamps, and controls the high and low beam shutter operation through high side drivers on the right and left high beam feed circuits. The BCM also sends the appropriate electronic headlamp beam status messages to the IPC to control the illumination of the high beam indicator.

The BCM also remembers which beams (LOW or HIGH) were selected when the headlamps were last turned OFF, and energizes those beams again the next time the headlamps are turned ON. The BCM provides a battery saver (load shedding) feature for the headlamps, which will turn these lamps OFF if they are left ON for more than about eight minutes when the ignition switch status is LOCK. The SCCM and the BCM each provide a fail-safe feature for the headlamps, which will cause the BCM to turn the low beam headlamps ON automatically if there is no input available from the headlamp switch or the multi-function switch. The BCM also provides a fail-safe feature for the headlamps that will turn the headlamps ON automatically whenever a loss of CAN bus communication is detected when the ignition switch status is ON.

Each headlamp includes an integral reflector adjustment screw to be used for static aiming of the headlamps.