Jeep Grand Cherokee WK. Manual — part 658
IMPACT SENSOR
DESCRIPTION
FRONT
Two front impact sensors (1) are used on this model,
one each for the left and right sides of the vehicle.
These sensors are mounted remotely from the impact
sensor that is internal to the Occupant Restraint Con-
troller (ORC). Each front sensor is secured with two
flanged hex nuts to two studs on 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 (2), an integral anti-rota-
tion pin (3), and two integral mounting holes (4) with
metal sleeves to provide crush protection.
The right and left front impact sensors are identical in construction and calibration. A label on the sensor is imprinted
with an arrow, which should always be pointed forward in the vehicle. A cavity in the center of the molded plastic
impact sensor housing contains the electronic circuitry of the sensor which includes an electronic communication
chip and an electronic impact sensor. Potting material fills the cavity and a stamped cover (5) is crimped over the
cavity to seal and protect the internal electronic circuitry and components. The front impact sensors are each con-
nected to the vehicle electrical system through a dedicated take out and connector of the headlamp and dash wire
harness.
The impact sensors cannot be repaired or adjusted and, if damaged or faulty, they must be replaced.
SIDE
Four side impact sensors (2) are used on this model
when it is equipped with the optional side curtain air-
bags, two each for the left and right sides of the vehi-
cle. These sensors are mounted remotely from the
impact
sensor
that
is
internal
to
the
Occupant
Restraint Controller (ORC). Each side sensor is
secured with two screws to the inner right or left B-pil-
lar and C-pillar beneath the trim within the passenger
compartment. The sensor housing has an integral con-
nector receptacle (3), an integral anti-rotation pin (4),
and two integral mounting holes (1) with metal sleeves
to provide crush protection.
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RESTRAINTS - SERVICE INFORMATION
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The right and left side impact sensors are identical in construction and calibration. A label on the sensor is imprinted
with an arrow, which should always be pointed forward in the vehicle. A cavity in the center of the molded plastic
impact sensor housing contains the electronic circuitry of the sensor which includes an electronic communication
chip and an electronic impact sensor. Potting material fills the cavity and a stamped cover (5) is crimped over the
cavity to seal and protect the internal electronic circuitry and components. The side impact sensors are each con-
nected to the vehicle electrical system through a dedicated take out and connector of the body wire harness.
The impact sensors cannot be repaired or adjusted and, if damaged or faulty, they must be replaced.
OPERATION
FRONT
The front impact sensors are electronic accelerometers that sense the rate of vehicle deceleration, which provides
verification of the direction and severity of an impact. Each sensor also contains an electronic communication chip
that allows the unit to communicate the sensor status as well as sensor fault information to the microprocessor in
the Occupant Restraint Controller (ORC).
The ORC microprocessor continuously monitors all of the passive restraint system electrical circuits to determine the
system readiness. If the ORC detects a monitored system fault, it sets a Diagnostic Trouble Code (DTC) and con-
trols 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 ORC. The impact sensors and the ORC commu-
nicate by modulating the voltage in the sensor plus circuit.
The hard wired circuits between the front impact sensors and the ORC may be diagnosed and tested using con-
ventional diagnostic tools and procedures. However, conventional diagnostic methods will not prove conclusive in
the diagnosis of the ORC, the impact sensors, or the electronic message inputs to or outputs from the impact sen-
sors. The most reliable, efficient, and accurate means to diagnose the impact sensors, the ORC, and the electronic
message communication between the sensors and the ORC requires the use of a diagnostic scan tool. Refer to the
appropriate diagnostic information.
SIDE
The side impact sensors are electronic accelerometers that sense the rate of vehicle deceleration, which provides
verification of the direction and severity of an impact. Each sensor also contains an electronic communication chip
that allows the unit to communicate the sensor status as well as sensor fault information to the microprocessor in
the Occupant Restraint Controller (ORC).
The ORC microprocessor continuously monitors all of the side passive restraint system electrical circuits to deter-
mine the system readiness. If the ORC 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 the same left or right sensor plus and minus circuits in a series arrangement from the ORC. The impact
sensors and the ORC communicate by modulating the voltage in the sensor plus circuit.
The hard wired circuits between the side impact sensors, and those between the sensors and the ORC may be
diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic meth-
ods will not prove conclusive in the diagnosis of the ORC, the impact sensors, or the electronic message inputs to
or outputs from the impact sensors. The most reliable, efficient, and accurate means to diagnose the impact sen-
sors, the ORC, and the electronic message communication between the sensors and the ORC requires the use of
a diagnostic scan tool. Refer to the appropriate diagnostic information.
REMOVAL
FRONT
WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, occupant classification sys-
tem, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect
and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge
before performing further diagnosis or service. This is the only sure way to disable the supplemental
restraint system. Failure to take the proper precautions could result in accidental airbag deployment.
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RESTRAINTS - SERVICE INFORMATION
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WARNING: To avoid personal injury or death, never strike or drop the front impact sensor, as it can damage
the impact sensor or affect its calibration. The front impact sensor enables the system to deploy the front
supplemental restraints. If an impact sensor is accidentally dropped during service, the sensor must be
scrapped and replaced with a new unit. Failure to observe this warning could result in accidental, incom-
plete, or improper front supplemental restraint deployment.
NOTE: The front and side impact sensors are interchangeable.
1. Disconnect and isolate the battery negative cable.
Wait two minutes for the system capacitor to dis-
charge before further service.
2. Remove the two nuts (1) that secure the right or
left front impact sensor (2) to the studs on the back
of the right or left radiator support vertical member.
3. Disconnect the headlamp and dash wire harness
connector (3) from the sensor connector recepta-
cle.
4. Remove the right or left front impact sensor from
the engine compartment.
SIDE - B-PILLAR
WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, occupant classification sys-
tem, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect
and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge
before performing further diagnosis or service. This is the only sure way to disable the supplemental
restraint system. Failure to take the proper precautions could result in accidental airbag deployment.
WARNING: To avoid personal injury or death, never strike or drop the side impact sensor, as it can damage
the impact sensor or affect its calibration. The side impact sensor enables the system to deploy the side
curtain supplemental restraints. If an impact sensor is accidentally dropped during service, the sensor must
be scrapped and replaced with a new unit. Failure to observe this warning could result in accidental, incom-
plete, or improper front supplemental restraint deployment.
NOTE: The front and side impact sensors are interchangeable.
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1. Adjust the driver or passenger side front seat to its
most forward position for easiest access to the
B-pillar trim.
2. Disconnect and isolate the battery negative cable.
Wait two minutes for the system capacitor to dis-
charge before further service.
3. Remove the trim from the inside of the lower right
or left B-pillar (1). (Refer to 23 - BODY/INTERIOR/
B-PILLAR LOWER TRIM - REMOVAL).
4. Remove the two screws (3) that secure the side
impact sensor (2) to the lower B-pillar.
5. Disconnect the body wire harness connector (4)
from the sensor connector receptacle.
6. Remove the sensor from the B-pillar.
SIDE - C-PILLAR
WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, occupant classification sys-
tem, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect
and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge
before performing further diagnosis or service. This is the only sure way to disable the supplemental
restraint system. Failure to take the proper precautions could result in accidental airbag deployment.
WARNING: To avoid personal injury or death, never strike or drop the side impact sensor, as it can damage
the impact sensor or affect its calibration. The side impact sensor enables the system to deploy the side
curtain supplemental restraints. If an impact sensor is accidentally dropped during service, the sensor must
be scrapped and replaced with a new unit. Failure to observe this warning could result in accidental, incom-
plete, or improper front supplemental restraint deployment.
NOTE: The front and side impact sensors are interchangeable.
WK
RESTRAINTS - SERVICE INFORMATION
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