Grand Cherokee 2WD V8-4.7L VIN J (2004)
Fig. 49 Side Impact Sensor
SIDE IMPACT SENSOR
On vehicles equipped with the optional side curtain airbags, two side impact sensors are used, one each for the left and right sides of the vehicle.
These sensors are mounted remotely from the bi-directional safing sensor that is internal to the Airbag Control Module (ACM). The side and front
impact sensors are identical in construction and calibration with the exception of the right-hand and left-hand die cast aluminum mounting brackets to
which each front impact sensor is secured with two screws. The side impact sensors are secured with two screws to the base of the right and left
B-pillars just below the front seat belt retractors and behind the lower B-pillar trim within the passenger compartment.
The impact sensor housing has an integral connector receptacle and two integral mounting ears, each with a metal sleeve to provide crush protection.
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 circuitry and
components. The side impact sensors are each connected to the vehicle electrical system through a dedicated take out and connector of the airbag
overlay wire harness.
The side impact sensors cannot be repaired or adjusted and, if damaged or faulty they must be replaced.
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 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 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 side 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 or the impact sensors. The most reliable, efficient, and accurate means to diagnose the impact sensors, the
ACM, and the electronic message communication between the sensors and the ACM requires the use of a DRBIII scan tool. Refer to the appropriate
diagnostic information.
