Jeep KJ 2005 Service Manual page 604

KJ
IMPACT SENSOR (Continued)
Fig. 28 Front Impact Sensor
1 - IMPACT SENSOR
2 - MOUNTING HOLE
3 - ANTI-ROTATION PIN
4 - CONNECTOR RECEPTACLE
an electronic impact sensor. Potting material fills the
cavity to seal and protect the internal electronic cir-
cuitry and components. The front impact sensors are
each connected 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
Fig. 29 Side Impact Sensor
1 - IMPACT SENSOR
2 - MOUNTING HOLE
3 - ANTI-ROTATION PIN
4 - CONNECTOR RECEPTACLE
Two side impact sensors are used on this model
when it is equipped with the optional side curtain
airbags, one each for the left and right sides of the
vehicle (Fig. 29). These sensors are mounted
remotely from the impact sensor that is internal to
the Airbag Control Module (ACM). Each side sensor
is secured with a screw to the inner right or left
B-pillar above the front seat belt retractor within the
passenger compartment. The sensor housing has an
integral connector receptacle, an integral anti-rota-
tion pin, and an integral mounting hole with a metal
sleeve to provide crush protection.
The right and left side impact sensors are identical
in construction and calibration. A cavity in the center
of the molded black 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 to seal and protect the internal electronic cir-
cuitry and components. The side impact sensors are
each connected 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 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 continuously monitors all
of the 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 opera-
tion accordingly. The impact sensors each receive bat-
tery 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 procedures.
However, conventional diagnostic methods will not
prove conclusive in the diagnosis of the ACM, 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
sensors, the ACM, and the electronic message com-
munication between the sensors and the ACM
requires the use of a diagnostic scan tool. Refer to
the appropriate diagnostic information.
RESTRAINTS 8O - 29