Impact Sensor: Description and Operation
IMPACT SENSORFRONT
Two front impact sensors (1) are used on this vehicle, 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 Controller (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-rotation 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 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 ineffective, they must be replaced.
SIDE
Six side impact sensors (1) are used on this vehicle with the side curtain airbags, three 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, the inner quarter panel near the C-pillar and the inner quarter panel near the D-pillar beneath the trim within the passenger compartment. The sensor housing has an integral connector receptacle (2), an integral anti-rotation pin (3), and two integral mounting holes (4) 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 outboard 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 ineffective, 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 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 ORC. The impact sensors and the ORC communicate 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 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.
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 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.