Low Beam Headlamps (Standard) RPO TT4

The headlamps consist of 2 interchangeable single filament bulbs or 2 high intensity discharge (HID) arc tubes and ballast on each side of the vehicle which provide high and low beams. The lower bulb in the headlamp is the high beam and the upper bulb is the low beam.

The headlamps may be turned ON in 3 different ways:

• When the headlamp switch is placed in the ON position, for normal operation
• When the headlamp switch is placed in the AUTOMATIC LIGHT position, for automatic lamp control
• When the headlamp switch is placed in the AUTOMATIC LIGHT position, with the windshield wipers ON in daylight conditions, after a 6 s delay

The body control module (BCM) controls the headlamps based on the inputs explained above. When a low beam request is received, the BCM supplies B+ to both low beam headlamps, illuminating the low beam headlamps.

When a high beam request is received, the BCM grounds the headlamp high beam relay control circuit. This energizes the coil in the headlamp high beam relay, causing the relay switch to close. This then applies B+ to both high beam headlamps through the left high beam and right high beam fuses, illuminating the high beam headlamps.