Air Bag Systems: Description and Operation

Supplementary Restraint Air Bag System







Airbag/SRS units provided for driver and front seat passenger protection, are installed in the center of the steering wheel, the passenger side fascia and the outer wing of each front seat. A single point sensing unit (SPS) mounted on the transmission tunnel, below the radio, provides fully electronic impact sensing, control and diagnostics for the front airbags Deployment of each side airbag is initiated by a side impact sensing module (SISM) installed in the adjacent 'B' post. Each SISM senses and electronically processes a crash pulse and if this exceeds the 'must fire' threshold, transmits a fire signal to the SPS unit. The SPS unit monitors whole vehicle motion and on confirmation of a crash condition, transmits a firing current pulse to the appropriate airbags. In the event of a side only impact, the SPS will send a current pulse to the airbag on the struck only. Neither the non-struck side airbag nor the frontal restraint system will be deployed under these conditions. The airbag system can only be activated when the ignition switch is in position II or III.