HEADLAMP SYSTEM
The headlamp system will default to headlamps
ON position when ignition switch is ON and when an
open or short circuit failure occurs on the headlamp
switch input or PCI data bus communication between
the BCM and the IPM fails. The system will return
to normal operation when the open or short is
repaired. A fault will be reported by the BCM when a
failure occurs on the dimmer or headlamp switch
input.
If the exterior lamps are ON and the headlamp
switch is in any position other than OFF or AUTO
and with the ignition switch OFF (LOCK) after 3
minutes the BCM sends a message via the PCI bus
to the IPM informing the IPM to turn off the head-
lamps, park lamps and fog lamps. This feature pre-
vents the vehicle battery from being discharged when
the vehicle lights have been left ON.
OPTICAL HORN/HIGH BEAMS
When the multi-function switch is pulled to the
first detent (optical horn) with the headlamps ON
and the key-in the ignition, the BCM shall send a
message via PCI bus to the IPM to turn on the head-
lamps drivers to illuminate all four filaments (Low
and High beams). When the multi-function switch is
pulled to the second detent (high beam) signal and
the headlamps are ON, the BCM shall send a mes-
sage via PCI bus to the IPM to turn on the head-
lamps drivers. The High Beams and Low Beams are
illuminated and the Fog Lamps (if ON) are extin-
guished. If the headlamps were in the high beam
configuration when power was removed from the
headlamps, the headlamps will be configured as low
beam the next time they are activated.
HEADLAMP SWITCH
The Headlamp Switch uses a multiplexed (MUX)
circuit to the Body Control Module (BCM). The Head-
lamp Switch controls the Fog lamp relay, Park lamps
and the Low and High beam headlamps. The BCM
then sends a signal through the PCI data bus line to
the IPM as to what state the switch has selected.
The IPM energizes the high side output drivers to
turn ON the desired lamps.
FRONT PARK and SIDE MARKER LAMPS
The park lamp switch is a direct input to the BCM.
The BCM sends a PCI data bus message to the IPM
informing it to turn on the park and side marker
lamps. The park lamp relay is then powered through
low side control of the IPM. This circuit is electroni-
cally controlled and continuously monitored for mal-
functions. The IPM provides power through a high
side driver.
HEADLAMP TIME DELAY SYSTEM
The headlamp time delay system is activated by
turning the headlamps ON (high or low beam) while
the engine is running, turning the ignition switch
OFF, and then turning the headlamp switch OFF
within 45 seconds. The system will not activate if
more than 45 seconds elapse between ignition switch
OFF and headlamp switch OFF. The BCM will allow
the headlamps to remain ON for 90 seconds (config-
urable) before they automatically turn off (if the key
is in the ignition during the headlamp time delay
mode, then both the headlamps and park lamps
(including panel dimming) will be ON).
If the headlamp switch is in the Auto Headlamp
Position, the headlamps are ON due to the night sig-
nal from the CMTC and the ignition switch is in any
position other than run/start, the BCM shall enter a
90 second (configurable) Auto Headlamps time delay
mode. If the key is in the ignition during the head-
lamp time delay mode, then both the headlamps and
park lamps (including panel dimming) will be ON. If
the key is not in the ignition, then only the head-
lamps will be ON. The BCM will allow the head-
lamps to remain ON for 90 seconds before they
automatically turn OFF.
FRONT FOG LAMP
The fog lamp switch is a direct input to the BCM.
The BCM sends a PCI data bus message to the IPM
informing it to turn on the fog lamps. This circuit is
electronically controlled and continuously monitored
for malfunctions. Fog lamp functionality is not
equipped on all vehicles. The IPM
9learns9 that the
vehicle is equipped with fog lamps by reading the
BCM data bus message. The Fog lamps can only be
ON when the park and low beams are ON. If the
high beams are switched ON then the Fog lamps will
be automatically turned OFF.
EXTERIOR LIGHTING BATTERY SAVER
The BCM monitors the status of the control of the
Park Lamps, Headlamps and Fog Lamps. If any exte-
rior lamps are left ON after the ignition is turned
OFF, the BCM will send this information to the IPM
which will then turn the drivers OFF after 3 min-
utes.
AUTOMATIC HEADLAMPS
Automatic headlamps are controlled by the Body
Control Module (BCM). With the headlamp switch in
the AUTO position, the BCM will control the head-
lamp, parking, side marker, tail and instrumentation
lamps based on ambient light levels. Ambient light
levels are monitored by the BCM using the Day/
Night signal and Electrochromatic Mirror (ECM)
present from the Compass Mini Trip (CMTC) located
CS
LAMPS/LIGHTING - EXTERIOR
8L - 3
LAMPS/LIGHTING - EXTERIOR (Continued)