2002 JEEP LIBERTY radiator

(2) Remove the radio from the instrument panel.
(Refer to 8 - ELECTRICAL/AUDIO/RADIO -
REMOVAL).
(3) Remove the screw at the top of the instrument
panel radio opening that secures the hazard switch
to the instrument panel trim (Fig. 22).
(4) Reach through and above the instrument panel
radio opening to access the two latch tabs of the
stamped metal hazard switch mounting bracket.
(5) Using two fingertips, pull rearward and down-
ward on the latch tabs on the back of the hazard
switch until it is disengaged from the instrument
panel trim.
(6) Push the hazard switch button through the
button opening of the instrument panel far enough to
disengage the alignment pins on each side of the
switch housing from the saddle formations of the two
stanchions on the back of the instrument panel trim,
just below and to either side of the button opening.
(7) Disconnect the instrument panel wire harness
connector for the hazard switch from the switch con-
nector receptacle.
(8) Remove the hazard switch through the instru-
ment panel radio opening.
INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Position the hazard switch through the instru-
ment panel radio opening.
(2) Reconnect the instrument panel wire harness
connector for the hazard switch to the switch connec-
tor receptacle.
(3) Reach through and above the instrument panel
radio opening to position the hazard switch for
installation.
(4) Guide the hazard switch button through the
button opening of the instrument panel, which will
engage the alignment pins on each side of the switch
housing with the saddle formations of the two stan-
chions on the back of the instrument panel trim, just
below and to either side of the button opening.
(5) Using hand pressure, press upward on the
back of the hazard switch until the latch tabs of the
mounting bracket on the back of the switch are both
engaged with the instrument panel trim (Fig. 22).
(6) Install and tighten the screw at the top of the
instrument panel radio opening that secures the haz-
ard switch to the instrument panel trim. Tighten the
screw to 2 N´m (17 in. lbs.).
(7) Reinstall the radio into the instrument panel.
(Refer to 8 - ELECTRICAL/AUDIO/RADIO -
INSTALLATION).
(8) Reconnect the battery negative cable.
HEADLAMP BULB
REMOVAL
NORTH AMERICA
(1) Disconnect and isolate the battery negative
cable.
(2) Reach behind the headlamp unit from the
engine compartment side of the upper radiator cross-
member to access the headlamp bulb lock ring (Fig.
23).
(3) Firmly grasp the lock ring on the back of the
headlamp unit housing.
Fig. 22 Hazard Switch Remove/Install
1 - WIRE HARNESS CONNECTOR
2 - HAZARD SWITCH
3 - ALIGNMENT PIN (2)
4 - STANCHION (2)
5 - INSTRUMENT PANEL
6 - SCREW (1)
7 - MOUNTING BRACKET LATCH TAB (2)
8Ls - 30 LAMPSKJ
HAZARD SWITCH (Continued)

(4) Rotate the lock ring on the back of the head-
lamp unit housing counterclockwise about 30
degrees.
CAUTION: Do not contaminate the bulb glass by
touching it with your fingers or by allowing it to
contact other oily surfaces. Shortened bulb life will
result.
(5) Pull the lock ring, socket, and bulb straight out
of the headlamp unit housing and up from behind
the upper radiator crossmember (Fig. 24).(6) Disconnect the grille opening reinforcement
wire harness connector for the headlamp bulb from
the connector receptacle on the bulb socket.
(7) Remove the bulb and bulb socket from the lock
ring as a unit.
REST-OF-WORLD
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the headlamp unit from the grille
opening reinforcement. (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - EXTERIOR/HEADLAMP UNIT
- REMOVAL).
(3) Firmly grasp the tab of the headlamp boot seal
on the back of the headlamp unit housing (Fig. 25).
(4) Pull the tab away from the back of the head-
lamp unit housing to remove the boot seal from the
housing and the bulb base.
(5) Pinch the two hooked ends of the wire head-
lamp bulb retainer clip together and disengage them
from the slots in the flange of the reflector (Fig. 26).
(6) Pivot the headlamp bulb retainer clip up off of
the bulb flange and out of the way.
CAUTION: Do not contaminate the bulb glass by
touching it with your fingers or by allowing it to
contact other oily surfaces. Shortened bulb life will
result.
Fig. 23 Headlamp Bulb Lock Ring
1 - HEADLAMP UNIT HOUSING
2 - LOCK RING
3 - SOCKET & BULB
Fig. 24 Headlamp Bulb Remove/Install
1 - HEADLAMP BULB
2 - SOCKET
3 - LOCK RING
Fig. 25 Headlamp Bulb Boot Seal Remove
1 - LEVELING MOTOR (IF EQUIPPED)
2 - BOOT SEAL
3 - FRONT POSITION LAMP
4 - ADJUSTING SCREW
5-TAB
6 - BULB BASE
KJLAMPS8Ls-31
HEADLAMP BULB (Continued)

(7) Pull the bulb straight out of the headlamp unit
reflector (Fig. 27).
INSTALLATION
NORTH AMERICA
CAUTION: Always use the correct bulb size and
type for replacement. An incorrect bulb size or type
may overheat and cause damage to the lamp, the
socket and/or the lamp wiring.
CAUTION: Do not contaminate the bulb glass by
touching it with your fingers or by allowing it to
contact other oily surfaces. Shortened bulb life will
result.
(1) Position the headlamp bulb and socket unit
into the lock ring (Fig. 24).
(2) Reconnect the grille opening reinforcement
wire harness connector for the headlamp bulb to the
connector receptacle on the bulb socket.
(3) Position the lock ring, socket, and bulb down
behind the upper radiator crossmember and align
them with the socket opening on the back of the
headlamp unit housing.
(4) Push the socket and bulb straight into the
headlamp unit housing until they are firmly seated.
(5) Position the lock ring over the socket and
engage it with the flange on the back of the head-
lamp unit housing (Fig. 23).
(6) Rotate the lock ring on the back of the head-
lamp unit housing clockwise about 30 degrees.
(7) Reconnect the battery negative cable.
REST-OF-WORLD
CAUTION: Always use the correct bulb size and
type for replacement. An incorrect bulb size or type
may overheat and cause damage to the lamp, the
socket and/or the lamp wiring.
CAUTION: Do not contaminate the bulb glass by
touching it with your fingers or by allowing it to
contact other oily surfaces. Shortened bulb life will
result.
(1) Position the bulb into the headlamp unit reflec-
tor (Fig. 27).
(2) Pivot the headlamp bulb retainer clip back over
the bulb flange.
(3) Pinch the two hooked ends of the wire head-
lamp bulb retainer clip together and engage them
into the slots in the flange of the reflector (Fig. 26).
(4) Position the center opening of the boot seal
over the base of the headlamp bulb and pull it down-
ward until the seal is fully engaged over the bulb
base (Fig. 25).
Fig. 26 Headlamp Bulb Retainer Clip Engage/
Disengage
1 - RETAINER CLIP
2 - BULB BASE
3 - HEADLAMP HOUSING
4 - REFLECTOR
5 - BULB FLANGE
6 - RETAINER SLOTS
Fig. 27 Headlamp Bulb Remove/Install
1 - BULB BASE
2 - RETAINER CLIP
3 - LEVELING MOTOR (IF EQUIPPED)
4 - REFLECTOR
5 - HEADLAMP HOUSING
6 - BULB FLANGE
8Ls - 32 LAMPSKJ
HEADLAMP BULB (Continued)

below the headlamp horizontal centerline for vehicles
in North America, or from just below horizontal to
125 millimeters (5 inches) below the headlamp hori-
zontal centerline for vehicles in Rest-Of-World.
(4) Repeat the adjustment procedure for the oppo-
site headlamp.
LICENSE PLATE LAMP BULB
REMOVAL
NORTH AMERICA
(1) Disconnect and isolate the battery negative
cable.
(2) Reach through the opening in the rear bumper
fascia between the license plate and the lamp to
access and firmly grasp the socket on the back of the
license plate lamp unit housing (Fig. 45).
(3) Pull the socket and bulb straight out of the
back of the license plate lamp unit housing.
(4) Pull the bulb straight out of the license plate
lamp unit socket.
REST-OF-WORLD
(1) Disconnect and isolate the battery negative
cable.
(2) Unsnap and lift up the bottom of the license
mounting plate far enough to access and remove the
two screws that secure the license plate bracket to
the special lug nuts on the spare tire (Fig. 46).
(3) Swing the license plate bracket away from the
spare tire far enough to access the license plate lamp
bulb sockets.(4) Firmly grasp the socket on the top of the
license plate lamp unit housing for the bulb that is
being removed (Fig. 47).
(5) Rotate the socket on the top of the license plate
lamp unit housing counterclockwise about 30
degrees.
(6) Pull the socket and bulb straight out of the top
of the license plate lamp unit housing.
(7) Pull the bulb straight out of the license plate
lamp unit socket.
Fig. 44 Headlamp Adjusting Screw
1 - HEADLAMP UNIT
2 - FENDER PANEL
3 - ADJUSTING SCREW ACCESS HOLE
4 - UPPER RADIATOR CROSSMEMBER
Fig. 45 License Plate Lamp Bulb Remove/Install -
North America
1 - REAR BUMPER FASCIA
2 - LICENSE PLATE LAMP
3 - SOCKET
4 - BULB
Fig. 46 License Plate Bracket - Rest-Of-World
1 - SPARE TIRE
2 - SPECIAL LUG NUT (2)
3 - LICENSE PLATE BRACKET
4 - SCREW (2)
8Ls - 44 LAMPSKJ
HEADLAMP UNIT (Continued)

NOTE: Individual channels cannot be erased. Eras-
ing the transmitter codes will erase ALL pro-
grammed codes.
STANDARD PROCEDURE - SETTING
TRANSMITTER CODES
(1) Turn off the engine.
(2) Erase the factory test codes by pressing but-
tons 1 and 3. Release the buttons when the two
green lights begin to flash (about 20 seconds).
(3) Choose one of the three buttons to train. Place
the hand-held transmitter within one inch of the uni-
versal transmitter and push the buttons on both
transmitters. The green dot below the house symbol
will begin to flash slowly.
(4) When the red light on the universal transmit-
ter begins to flash rapidly (this may take as long as
60 seconds), release both buttons. Your universal
transmitter is now ªtrainedº. To train the other but-
tons, repeat Step 3 and Step 4. Be sure to keep your
hand-held transmitter in case you need to retrain the
universal transmitter.
AMBIENT TEMP SENSOR
DESCRIPTION
Ambient air temperature is monitored by the Com-
pass Mini-Trip Computer (CMTC) through ambient
temperature sensor messages received from the Body
Control Module (BCM) over the Programmable Com-
munications Interface (PCI) data bus network. The
BCM receives a hard wired input from the ambient
temperature sensor. The ambient temperature sensor
(Fig. 8) is a variable resistor mounted in front the
radiator, behind the grille, near the center of the
vehicle.
Refer toBody Control Modulein Electronic Con-
trol Modules. For complete circuit diagrams, refer to
the appropriate wiring information. The ambient
temperature sensor cannot be adjusted or repaired
and, if faulty or damaged, it must be replaced.
OPERATION
The ambient temperature sensor is a variable
resistor that operates on a five-volt reference signal
sent to it by the BCM. The resistance in the sensor
changes as temperature changes, changing the tem-
perature sensor signal circuit voltage to the BCM.
Based upon the resistance in the sensor, the BCM
senses a specific voltage on the temperature sensor
signal circuit, which it is programmed to correspond
to a specific temperature. The BCM then sends the
proper ambient temperature messages to the CMTC
over the PCI data bus.
The thermometer function is supported by the
ambient temperature sensor, a wiring circuit, the
Body Control Module (BCM), the Programmable
Communications Interface (PCI) data bus, and a por-
tion of the Compass Mini-Trip Computer module.
The ambient temperature sensor circuit can also be
diagnosed by referring toDiagnosis and Testing -
Ambient Temperature Sensor, and Diagnosis
and Testing - Ambient Temperature Sensor Cir-
cuit. If the temperature sensor and circuit are con-
firmed to be OK, but the temperature display is
inoperative or incorrect, refer toDiagnosis and
Testing - Compass Mini-Trip Computerin this
section. For complete circuit diagrams, refer to the
appropriate wiring information.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector.
(2) Measure the resistance of the ambient temper-
ature sensor. At ±40É C (±40É F), the sensor resis-
tance is 336 kilohms. At 55É C (140É F), the sensor
resistance is 2.488 kilohms. The sensor resistance
should read between these two values. If OK, refer to
Diagnosis and Testing - Ambient Temperature
Sensor Circuitin this group. If not OK, replace the
faulty ambient temperature sensor.
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR CIRCUIT
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector and the Body Control Module wire
harness connector.
(2) Connect a jumper wire between the two termi-
nals in the body half of the ambient temperature sen-
sor wire harness connector.
Fig. 8 Ambient Temperature Sensor
KJMESSAGE SYSTEMS 8M - 9
UNIVERSAL TRANSMITTER (Continued)

is located on the back side of each vertical member of
the radiator support.
²Passenger Airbag- The passenger airbag is
located on the instrument panel, beneath the passen-
ger airbag door on the instrument panel above the
glove box on the passenger side of the vehicle.
²Passenger Knee Blocker- The passenger knee
blocker is a structural reinforcement that is integral
to and concealed within the glove box door.
²Seat Belt Tensioner- The seat belt tensioner
is integral to the driver side front seat belt retractor
unit on vehicles equipped with dual front airbags.
²Side Impact Airbag Control Module-Two
Side Impact Airbag Control Modules (SIACM) are
used on vehicles with the optional side curtain air-
bags, one left side and one right side. One SIACM is
located behind the B-pillar trim near the base of each
B-pillar.
²Side Curtain Airbag- In vehicles equipped
with this option, a side curtain airbag is located on
each inside roof side rail above the headliner, and
extends from the A-pillar to just beyond the C-pillar.
The ACM, both SIACMs, and the EMIC each con-
tain a central processing unit and programming that
allow them to communicate with each other using
the Programmable Communication Interface (PCI)
data bus network. This method of communication is
used by the ACM for control of the airbag indicator
on all models equipped with dual front airbags.
(Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/COMMUNICATION - DESCRIP-
TION).
Hard wired circuitry connects the supplemental
restraint system components to each other through
the electrical system of the vehicle. These hard wired
circuits are integral to several wire harnesses, which
are routed throughout the vehicle and retained by
many different methods. These circuits may be con-
nected to each other, to the vehicle electrical system,
and to the supplemental restraint system compo-
nents through the use of a combination of soldered
splices, splice block connectors, and many different
types of wire harness terminal connectors and insu-
lators. Refer to the appropriate wiring information.
The wiring information includes wiring diagrams,
proper wire and connector repair procedures, further
details on wire harness routing and retention, as well
as pin-out and location views for the various wire
harness connectors, splices and grounds.
OPERATION
ACTIVE RESTRAINTS The primary passenger
restraints in this or any other vehicle are the stan-
dard equipment factory-installed seat belts. Seat
belts are referred to as an active restraint because
the vehicle occupants are required to physically fas-ten and properly adjust these restraints in order to
benefit from them. See the owner's manual in the
vehicle glove box for more information on the fea-
tures, use and operation of all of the factory-installed
active restraints.
PASSIVE RESTRAINTS The passive restraints
system is referred to as a supplemental restraint sys-
tem because they were designed and are intended to
enhance the protection for the vehicle occupants of
the vehicleonlywhen used in conjunction with the
seat belts. They are referred to as passive systems
because the vehicle occupants are not required to do
anything to make them operate; however, the vehicle
occupants must be wearing their seat belts in order
to obtain the maximum safety benefit from the facto-
ry-installed supplemental restraint systems.
The supplemental restraint system electrical cir-
cuits are continuously monitored and controlled by a
microprocessor and software contained within the
Airbag Control Module (ACM) and, on vehicles
equipped with the side curtain airbags, both Side
Impact Airbag Control Modules (SIACM). An airbag
indicator in the ElectroMechanical Instrument Clus-
ter (EMIC) illuminates for about seven seconds as a
bulb test each time the ignition switch is turned to
the On or Start positions. Following the bulb test,
the airbag indicator is turned on or off by the ACM
to indicate the status of the supplemental restraint
system. If the airbag indicator comes on at any time
other than during the bulb test, it indicates that
there is a problem in the supplemental restraint sys-
tem electrical circuits. Such a problem may cause air-
bags not to deploy when required, or to deploy when
not required.
Deployment of the supplemental restraints
depends upon the angle and severity of an impact.
Deployment is not based upon vehicle speed; rather,
deployment is based upon the rate of deceleration as
measured by the forces of gravity (G force) upon the
impact sensors. When an impact is severe enough,
the microprocessor in the ACM or the SIACM signals
the inflator unit of the airbag module to deploy the
airbag. The seat belt tensioner is provided with a
deployment signal by the ACM in conjunction with
the driver airbag. During a frontal vehicle impact,
the knee blockers work in concert with properly fas-
tened and adjusted seat belts to restrain both the
driver and the front seat passenger in the proper
position for an airbag deployment. The knee blockers
also absorb and distribute the crash energy from the
driver and the front seat passenger to the structure
of the instrument panel. The seat belt tensioner
removes the slack from the driver side front seat belt
to provide further assurance that the driver is prop-
erly positioned and restrained for an airbag deploy-
ment.
8O - 4 RESTRAINTSKJ
RESTRAINTS (Continued)

The ACM housing also has an integral ground lug
with a tapped hole that protrudes from the lower left
rear corner of the unit. This lug provides a case
ground to the ACM when a ground screw is installed
through the left side of the mounting bracket. Two
molded plastic electrical connector receptacles exit
the right side of the ACM housing. The smaller of the
two receptacles contains twelve terminal pins, while
the larger one contains twenty-three. These terminal
pins connect the ACM to the vehicle electrical system
through two dedicated take outs and connectors of
the instrument panel wire harness.
A molded rubber protective cover is installed
loosely over the ACM to protect the unit from con-
densation or coolant leaking from a damaged or
faulty heater-air conditioner unit housing. An inte-
gral flange on the left side of the cover is secured to
the floor panel transmission tunnel with a short
piece of double-faced tape as an assembly aid during
the manufacturing process, but this tape does not
require replacement following service removal.
The impact sensor and safing sensor internal to
the ACM are calibrated for the specific vehicle, and
are only serviced as a unit with the ACM. The ACM
cannot be repaired or adjusted and, if damaged or
faulty, it must be replaced. The ACM cover is avail-
able for separate service replacement.
OPERATION
The microprocessor in the Airbag Control Module
(ACM) contains the front supplemental restraint sys-
tem logic circuits and controls all of the front supple-
mental restraint system components. The ACM uses
On-Board Diagnostics (OBD) and can communicate
with other electronic modules in the vehicle as well
as with the DRBIIItscan tool using the Programma-
ble Communications Interface (PCI) data bus net-
work. This method of communication is used for
control of the airbag indicator in the ElectroMechani-
cal Instrument Cluster (EMIC) and for supplemental
restraint system diagnosis and testing through the
16-way data link connector located on the driver side
lower edge of the instrument panel. (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER/AIRBAG
INDICATOR - OPERATION).
The ACM microprocessor continuously monitors all
of the front supplemental restraint system electrical
circuits to determine the system readiness. If the
ACM detects a monitored system fault, it sets an
active and stored Diagnostic Trouble Code (DTC) and
sends electronic messages to the EMIC over the PCI
data bus to turn on the airbag indicator. An active
fault only remains for the duration of the fault or in
some cases the duration of the current ignition
switch cycle, while a stored fault causes a DTC to be
stored in memory by the ACM. For some DTCs, if afault does not recur for a number of ignition cycles,
the ACM will automatically erase the stored DTC.
For other internal faults, the stored DTC is latched
forever.
On models equipped with optional side curtain air-
bags, the ACM communicates with both the left and
right Side Impact Airbag Control Modules (SIACM)
over the PCI data bus. The SIACM notifies the ACM
when it has detected a monitored system fault and
stored a DTC in memory for its respective side cur-
tain airbag system, and the ACM sets a DTC and
controls the airbag indicator operation accordingly.
The ACM also monitors a Hall effect-type seat belt
switch located in the buckle of each front seat belt to
determine whether the seatbelts are buckled, and
provides an input to the EMIC over the PCI data bus
to control the seatbelt indicator operation based upon
the status of the driver side front seat belt switch.
The ACM receives battery current through two cir-
cuits; a fused ignition switch output (run) circuit
through a fuse in the Junction Block (JB), and a
fused ignition switch output (run-start) circuit
through a second fuse in the JB. The ACM has a case
ground through a lug on the bottom of the ACM
housing that is secured with a ground screw to the
left side of the ACM mounting bracket. The ACM
also receives a power ground through a ground cir-
cuit and take out of the instrument panel wire har-
ness. This take out has a single eyelet terminal
connector that is secured by a second ground screw
to the left side of the ACM mounting bracket. These
connections allow the ACM to be operational when-
ever the ignition switch is in the Start or On posi-
tions. The ACM also contains an energy-storage
capacitor. When the ignition switch is in the Start or
On positions, this capacitor is continually being
charged with enough electrical energy to deploy the
airbags for up to one second following a battery dis-
connect or failure. The purpose of the capacitor is to
provide backup supplemental restraint system pro-
tection in case there is a loss of battery current sup-
ply to the ACM during an impact.
Two sensors are contained within the ACM, an
electronic impact sensor and a safing sensor. The
ACM also monitors inputs from two remote front
impact sensors located on the back of the right and
left vertical members of the radiator support near
the front of the vehicle. The electronic impact sensors
are accelerometers that sense the rate of vehicle
deceleration, which provides verification of the direc-
tion and severity of an impact. The safing sensor is
an electromechanical sensor within the ACM that
provides an additional logic input to the ACM micro-
processor. The safing sensor is a normally open
switch that is used to verify the need for an airbag
deployment by detecting impact energy of a lesser
8O - 10 RESTRAINTSKJ
AIRBAG CONTROL MODULE (Continued)

FRONT IMPACT SENSOR
DESCRIPTION
Two front impact sensors are used on this model,
one each for the left and right sides of the vehicle
(Fig. 17). These sensors are mounted remotely from
the impact sensor that is internal to the Airbag Con-
trol Module (ACM). Each front sensor is secured with
two screws to the backs of the right and left vertical
members of the radiator support within the engine
compartment. The sensor housing has an integral
connector receptacle and two integral mounting
points each with a metal sleeve to provide crush pro-
tection.
The right and left front impact sensors are identi-
cal in construction and calibration with two excep-
tions:
²On models equipped with an optional 2.4L gaso-
line engine, the left front impact sensor includes a
shim that moves the sensor three millimeters toward
the rear of the vehicle on the left vertical member of
the radiator support for additional clearance that is
required for that application.
²On models equipped with an optional diesel
engine, the left front impact sensor includes a
stamped metal mounting bracket that rotates theconnector receptacle end of the sensor toward the
outboard side of the vehicle for additional clearance
that is required for that application.
A cavity in the center of the molded black plastic
impact sensor housing contains the electronic cir-
cuitry of the sensor which includes an electronic com-
munication chip and an electronic impact sensor.
Potting material fills the cavity to seal and protect
the internal electronic circuitry and components. The
front impact sensors are each connected to the vehi-
cle electrical system through a dedicated take out
and connector of the headlamp and dash wire har-
ness.
The impact sensors cannot be repaired or adjusted
and, if damaged or faulty, they must be replaced. The
mounting bracket for the left front impact sensor on
models with a diesel engine is serviced as a unit with
that sensor.
OPERATION
The front impact sensors are electronic accelerom-
eters that sense the rate of vehicle deceleration,
which provides verification of the direction and sever-
ity of an impact. Each sensor also contains an elec-
tronic communication chip that allows the unit to
communicate the sensor status as well as sensor
fault information to the microprocessor in the Airbag
Control Module (ACM). The ACM microprocessor con-
tinuously monitors all of the front passive restraint
system electrical circuits to determine the system
readiness. If the ACM detects a monitored system
fault, it sets a Diagnostic Trouble Code (DTC) and
controls the airbag indicator operation accordingly.
The impact sensors each receive battery current and
ground through dedicated left and right sensor plus and
minus circuits from the ACM. The impact sensors and
the ACM communicate by modulating the voltage in the
sensor plus circuit. The hard wired circuits between the
front impact sensors and the ACM may be diagnosed
and tested using conventional diagnostic tools and pro-
cedures. However, conventional diagnostic methods will
not prove conclusive in the diagnosis of the ACM or the
impact sensors. The most reliable, efficient, and accu-
rate means to diagnose the impact sensors, the ACM,
and the electronic message communication between the
sensors and the ACM requires the use of a DRBIIIt
scan tool. Refer to the appropriate diagnostic informa-
tion.
Fig. 17 Front Impact Sensor
1 - SENSOR
2 - CONNECTOR RECEPTACLE
KJRESTRAINTS 8O - 21