FTP
With the headlamps in the low beam position, you may momentarily turn ON or flash the high beams
using the dimmer switch handle. When you pull the headlamp dimmer switch handle toward you, the
flash-to-pass (FTP) switch closes, grounding the high beam circuit at G201. Both high beams will remain
ON until you release the switch handle. If the low beam headlamps were ON during an FTP operation, the
headlamps will remain ON.
Lights On Warning
The radio activates the lights on warning as requested by the body control module (BCM). The BCM sends
a class 2 message to the radio indicating the chime frequency (fast rate) and duration (continuous).
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The BCM determines that the driver's door is open (signal circuit is low).
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The BCM determines that the headlamp switch is in the park or head position.
Daytime Running Lamps (DRL)
The ambient light sensor is a light-sensitive transistor that varies its voltage signal to the body control
module (BCM) in response to changes in the outside (ambient) light level. When the BCM receives this
signal, the BCM turns ON either the DRL lamps or the headlamp relay for auto headlamp operation. Any
function or condition that turns ON the headlamps will cancel the DRL operation.
Thirty seconds after you start the ignition with the headlamp switch set in the OFF position, the DRL will
perform one of two actions:
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Illuminate the high beam headlamps at a reduced intensity in daylight conditions
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Illuminate the low beam headlamps in low light conditions
Battery positive voltage is applied at all times from the DRL/EXT LTS fuse in the underhood junction block
to the coil side of the DRL relay. When the ambient light sensor indicates a day light condition, the BCM
applies a ground to the DRL relay control circuit. This energizes the DRL relay allowing a ground to be
applied from G101 through the DRL relay switch side to the left high beam headlamp. When the DRL relay
is energized, battery positive voltage is applied from the EXT LTS fuse through the right high beam
headlamp, to the left high beam headlamp. The high beam headlamps are now in series, and split the
voltage so that the headlamps illuminate a half intensity. The DRL operates when the ignition switch is in
the RUN position, and the parking brake is not set or the transmission is not in park. When these
conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will
illuminate.
Fog Lamps
When the ignition switch is in the ON position and the headlamp switch is in either PARK or HEAD position,
the fog lights illuminate whenever you press the fog lamp switch. The FOG RLY fuse in the top of the
engine fuse block supplies battery positive voltage to both the fog lamp relay switch contacts and to the
fog lamp relay coil circuit. The fog lamp relay coil is controlled by the Body Control Module (BCM).
Whenever you press the fog lamp switch, the BCM fog lamp switch input is grounded. The BCM energizes
the control circuit of the fog lamp relay coil. The current flows from the fog lamp relay to both front fog
lamps and to ground G101. The fog lamps remain ON until you again press the front fog lamp switch, or
until you cycle the ignition switch OFF and ON. The park lamps or low beam headlamps must be ON in
order for the fog lamps to be illuminated. Fog lamp operation will be cancelled whenever the park lamps
are turned OFF or the high beam headlamps have been selected.
