Impact Sensor: Description and Operation

FORWARD (DISCRIMINATING) SENSOR
The forward (discriminating) sensor is used by the SDM to determine whether or not certain frontal crashes require deployment of the air bags. The sensor consists of a sensing element, normally open switch contacts and a diagnostic resistor. The sensing element closes the switch contacts when the vehicle velocity changes are severe enough to warrant deployment. The diagnostic resistor is connected in parallel with the switch contacts inside the sensor. The diagnostic resistor, in conjunction with resistors in the SDM, causes a voltage drop which allows the SDM to monitor the integrity of the forward (discriminating) sensor and associated circuitry.