Impact Sensor: Description and Operation

DESCRIPTION
Two impact sensors and a safing sensor provide verification of the direction and severity of an impact. The safing sensor is located inside the Airbag Control Module (ACM), which is mounted to a bracket on the floor transmission tunnel, under the instrument panel. The two impact sensors are mounted on the inner fender extension panels behind the grille opening reinforcement, on the left and right sides of the vehicle.

OPERATION
The impact sensors are threshold sensitive switches that complete an electrical circuit when an impact provides a sufficient deceleration force to close the switch. The safing sensor is an accelerometer that senses the rate of deceleration. The sensors are calibrated for the specific vehicle, and are sensitive to both the severity and the direction of an impact.

The microprocessor in the ACM monitors the sensor signals. A pre-programmed decision algorithm in the microprocessor determines when the deceleration rate indicates an impact that is severe enough to require airbag system protection. When the programmed conditions are met, the ACM sends an electrical signal to deploy the driver side airbag.

REPLACEMENT
The impact sensors and safing sensor cannot be repaired or adjusted and, if faulty or damaged, they must be replaced. The impact sensors are available for service replacement. The safing sensor is only serviced as part of the ACM.

CIRCUIT OPERATION
The airbag system uses two impact sensors. Circuits R47 and R49 connect from the left sensor to the Airbag Control Module (ACM). Circuits R46 and R48 connect the right sensor to the ACM.