switch feed circuit when the brake lamp switch is closed by the brake pedal arm. The CHMSL is connected to a
hard wired output from the brake lamp switch, while the brake lamps are controlled by an output from the Front
Control Module (FCM) based upon an input from the brake lamp switch.
DAYTIME RUNNING LAMPS
Vehicles manufactured for sale in Canada illuminate the high beam filament of both headlamp bulbs at a reduced
intensity when the engine is running and the exterior lamps are turned off. Fleet vehicles manufactured for sale in
the United States illuminate the low beam filament of both headlamp bulbs at a reduced intensity when the engine
is running, the parking brakes are released and the exterior lamps are turned off. The FCM must be programmed
appropriately for this feature to be enabled. Once enabled, anytime the FCM receives electronic messages over the
CAN data bus from the PCM indicating the engine is running and from the EMIC indicating the status of the head-
lamp switch exterior lighting input is Off and that the parking brakes are released, the FCM provides a pulse width
modulated voltage output to the proper headlamp bulb filaments through the right and left beam feed circuits to
produce illumination at a reduced intensity.
FRONT FOG LAMPS
Vehicles equipped with optional front fog lamps include a front fog lamp relay installed in the PDC, and a front fog
lamp switch integral to the headlamp switch on the instrument panel. The front fog lamps have a path to ground at
all times through their connection to the headlamp and dash wire harness. The headlamp and dash wire harness
has takeouts with eyelet terminals that are secured by ground screws to the right (right fog lamp) and left (left fog
lamp) inboard sides of the hydroform within the engine compartment. The EMIC monitors a hard wired multiplex
input from the headlamp switch to determine whether the fog lamps are selected, then sends electronic fog lamp
switch status messages to the FCM over the CAN data bus.
When the FCM receives a fog lamp status message it then controls front fog lamp operation by energizing or de-
energizing the front fog lamp relay control coil. The FCM also sends the appropriate electronic message back to the
EMIC to illuminate or extinguish the front fog lamp indicator. When the front fog lamp relay is energized, it provides
battery voltage from a fused B(+) fuse in the PDC to the fog lamps through the fog lamp relay output circuit. The
FCM will automatically de-energize the front fog lamps relay any time the headlamp high beams are selected. The
FCM also provides a battery saver (load shedding) feature for the front fog lamps, which will turn these lamps off if
they are left on for more than about eight minutes with the ignition switch in the Lock position. Each front fog lamp
includes an integral adjustment screw to be used for static aiming of the fog lamp beams.
HAZARD WARNING LAMPS
The hazard warning system includes the EMIC, the FCM and the multi-function switch on the steering column. The
EMIC monitors a hard wired multiplex input from the multi-function switch to determine the status of the hazard
warning switch, then sends the appropriate electronic hazard switch status messages to the FCM over the CAN
data bus. The FCM responds to these messages by controlling a battery voltage output and the flash rate for each
of the right and left turn signal lamps. The FCM also sends the appropriate electronic messages back to the EMIC
to control the illumination and flash rate of the right and left turn signal indicators, as well as to control the click rate
of an electromechanical relay soldered onto the EMIC electronic circuit board that emulates the sound emitted by a
conventional hazard warning flasher.
HEADLAMPS
The headlamp system includes the EMIC, the FCM, the multi-function switch on the steering column and the head-
lamp switch on the instrument panel. The headlamp bulbs have a path to ground at all times through their connec-
tion to the headlamp and dash wire harness. The headlamp and dash wire harness has takeouts with eyelet
terminals that are secured by ground screws to the right (right headlamp bulb) and left (left headlamp bulb) inboard
sides of the hydroform within the engine compartment.
The EMIC monitors a hard wired multiplex input to determine the status of the headlamp switch, and a hard wired
multiplex input from the multi-function switch to determine whether the high or low beams are selected. The EMIC
then sends the appropriate electronic headlamp switch and headlamp beam select switch status messages to the
FCM over the CAN data bus. The FCM responds to these messages by providing a pulse width modulated voltage
output to the proper headlamp bulb through the right and left low and high beam feed circuits to illuminate the
selected headlamp filaments.
The FCM 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 FCM 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
HB
LAMPS/LIGHTING - EXTERIOR - SERVICE INFORMATION
8L - 79