Impact Sensor: Description and Operation

PURPOSE
The front air bag sensors are electrical switches that react to frontal impacts according to direction and force. The primary sensors measure the crash severity.

OPERATION






Primary crash sensors are "hard-wired" to the air bags and operate in the following manner:
- They discriminate between impacts that require air bag inflation and impacts that do not.
- When an impact occurs that requires air bag inflation, the sensor contacts close, completing the electrical circuit necessary for system operation.
- The safing sensor and one primary crash sensor must be activated simultaneously to inflate the air bag.

The air bag system is designed to operate in frontal or front-angled collisions. The driver side air bag module and passenger side air bag module should activate in a crash with severe frontal deceleration, more severe than hitting a parked car of similar size and weight head-on at about 45 km/h (28 mph).

Because the air bag system senses severity of the crash rather than vehicle speed, some frontal collisions at speeds above 45 km/h (28 mph) may not be severe enough to require air bag inflation.

The sensors in the vehicle determine if air bag inflation is required in the following manner:
1. During severe frontal deceleration caused by an impact that decelerates the vehicle in the forward direction, both a radiator primary crash sensor and a safing sensor will activate.
2. When a primary and safing sensor are closed at the same time, electrical current will flow, igniting the driver side air bag module and passenger side air bag module.