Tail Lamp: Description and Operation

PARK, TAIL AND MARKER LAMPS

The park lamps consist of the park, tail, marker, and license lamps. These lamps are illuminated any time the headlamp switch is in the park, headlamp on position, or anytime the body control module (BCM) illuminates the headlamps. The PARK fuse in the fuse block - instrument panel (I/P) supplies voltage to both the coil and switch input side of the park lamp relay. The BCM controls the park lamp relay by grounding the park lamp control circuit energizing the relay.

For automatic lamp control (ALC) the BCM receives a signal from the ambient light sensor indicating a low or high ambient (outside) light level. Under low light conditions, the BCM grounds the park lamp relay control circuit energizing the park lamp relay. The now closed relay supplies voltage on the park lamp supply voltage circuit directly to the lamps. The BCM always turns ON the park lamps and headlamps together when in the ALC mode.

For manual operation, when the headlamp switch is in the park position, the headlamp switch supplies ground to the BCM on the park lamp switch signal circuit. In response, the BCM grounds only the park lamp relay control circuit, and the lamps illuminate as stated above.

The conditions necessary for the BCM to activate the ALC mode are as follows:
- The ignition switch is in the RUN position.
- The headlamps are in the OFF position.
- The park brake is released.
- The BCM is receiving a low light condition from the ambient light sensor, if equipped with RPO T 82.