SIR System Description

Schematic:

The SIR System consists of the Sensing and Diagnostic Module (SDM), the driver inflator module, the coil assembly, the passenger inflator module and the AIR BAG telltale in the instrument cluster. The SDM, coil assembly (driver's side only), driver inflator module, passenger inflator module and connecting wires make up the deployment loops. The function of the deployment loops is to supply current through the inflator modules, which will cause deployment of the air bags in the event of a frontal crash of sufficient force, up to 30 degrees left or right of the vehicle centerline. The inflator modules are only supplied enough current to deploy when the SDM detects vehicle velocity changes severe enough to warrant deployment.

The SDM contains a sensing device which converts the vehicles acceleration changes to an electrical signal. The electrical signal generated is processed by the SDM and then compared to values stored in Electrically Erasable Programmable Read Only Memory (EEPROM). When the proper thresholds are exceeded, the SDM will cause current to flow through the inflator modules deploying the air bags.