HEADLAMP SWITCH
DESCRIPTION
The headlamp switch is integral to the exterior
lighting switch, which is part of the left (lighting)
multi-function switch unit located on the left side of
the steering column. A knob on the end of the left
multi-function switch control stalk controls all of the
exterior lighting switch functions. The exterior light-
ing switch is hard wired to the Body Control Module
(BCM) through the instrument panel wire harness.
The exterior lighting switch cannot be adjusted or
repaired and, if faulty or damaged, the entire left
multi-function switch unit must be replaced. Refer to
Turn Signal and Hazard Warning Switch in the
Removal and Installation section of Group 8J - Turn
Signal and Hazard Warning Systems for the service
procedures. Refer to Body Control Module in the
Description and Operation section of Group 8E -
Instrument Panel Systems for more information on
this component. For complete circuit diagrams, refer
to Body Control Module in the Contents of Group
8W - Wiring Diagrams.
OPERATION
The exterior lighting switch uses a hard wired five
volt reference circuit from the BCM, resistor multi-
plexing and a hard wired switch output circuit in the
instrument panel wire harness to provide the BCM
with a zero to five volt signal that indicates the sta-
tus of all of the exterior lighting switch settings. The
BCM then uses control outputs to energize the head-
lamp and park lamp relays that activate the exterior
lighting circuits.
The BCM monitors the exterior lighting switch sta-
tus, then sends the proper switch status messages to
other electronic modules over the Programmable
Communications Interface (PCI) data bus network.
The exterior lighting switch status is also used by
the BCM as an input for chime warning system oper-
ation.
DIAGNOSIS AND TESTING
CHIME WARNING SYSTEM
Following are tests that will help to diagnose the
components and circuits that provide hard wired
inputs to the chime warning system. However, these
tests may not prove conclusive in the diagnosis of
this system. In order to obtain conclusive testing of
the chime warning system, the Programmable Com-
munications Interface (PCI) data bus network and all
of the electronic modules that provide inputs to, or
receive outputs from the chime warning system com-
ponents must be checked.
The most reliable, efficient, and accurate means to
diagnose the chime warning system requires the use
of a DRB scan tool and the proper Diagnostic Proce-
dures manual. The DRB scan tool can provide confir-
mation that the PCI data bus is functional, that the
Body Control Module (BCM) is sending and receiving
the proper messages on the PCI data bus, and that
the BCM is receiving the proper hard wired inputs to
perform its chime warning system functions.
DRIVER DOOR AJAR SWITCH
The driver door ajar switch is hard wired to the
Driver Door Module (DDM). The DDM communicates
the switch status to the other electronic modules in
the vehicle on the Programmable Communications
Interface (PCI) data bus network. Be certain that the
PCI data bus is functional before attempting diagno-
sis of the driver door ajar switch. A simple test to
confirm PCI data bus operation is to operate the pas-
senger side power mirror. If the passenger side power
mirror does not operate, use a DRB scan tool and the
proper Diagnostic Procedures manual to test the
operation of the PCI data bus and the DDM. If the
passenger side power mirror operates, the following
test will diagnose a faulty driver door ajar switch
and circuits. For complete circuit diagrams, refer to
Interior Lighting in the Contents of Group 8W -
Wiring Diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,
REFER
TO
GROUP
8M
-
PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING
WHEEL,
STEERING
COLUMN,
OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Check that the interior lighting switch on the
control stalk of the left multi-function switch is not
in the dome lamp disable position. Open the driver
side front door and note whether the interior lamps
light. They should light. If OK, refer to Key-In Igni-
tion Switch in the Diagnosis and Testing section of
this group for further diagnosis of the chime warning
system. If not OK, go to Step 2.
(2) Disconnect and isolate the battery negative
cable. Remove the trim panel from the driver side
front door and disconnect the 4-way door wire har-
ness connector from the front door latch connector
receptacle. Check for continuity between the ground
circuit cavity of the 4-way door wire harness connec-
tor for the front door latch and a good ground. There
should be continuity. If OK, go to Step 3. If not OK,
repair the ground circuit to ground as required.
8U - 4
CHIME/BUZZER WARNING SYSTEMS
WJ
DESCRIPTION AND OPERATION (Continued)