Grand Cherokee 2WD V8-5.7L VIN 2 (2005)
Impact Sensor: Description and Operation
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
vehicle. 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-pillar and C-pillar beneath the trim within the passenger compartment. The sensor housing has an
integral connector receptacle (3), an integral anti-rotation pin (4), and two integral mounting holes (1) with metal sleeves to provide crush protection.
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 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.
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 determine 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 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 sensors. 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.
