System Description

The SIR system consists of the following components:
^ Inflatable Restraint Sensing and Diagnostic Module (SDM)
^ Inflatable Restraint Steering Wheel Module
^ Inflatable Restraint Steering Wheel Module Coil
^ Inflatable Restraint Instrument Panel (IP) module
^ Inflatable Restraint IP module switch
^ Inflatable Restraint front end discriminating sensor
^ AIR BAG warning lamp in the instrument cluster
The Inflatable Restraint Sensing and Diagnostic Module (SDM), Inflatable Restraint Steering Wheel Module Coil (SIR coil assembly), Inflatable Restraint Steering Wheel Module (driver inflator module), Inflatable Restraint IP module (passenger inflator module), and connector 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. Deployment occurs when the SDM detects vehicle velocity changes severe enough to warrant deployment.
The SDM contains a sensing device (Accelerometer) that converts vehicle velocity changes to an electrical signal. The SDM compares this electrical signal to a value stored in memory. When the generated signal exceeds the stored value, the SDM performs additional signal processing and compares the generated signals to values stored in memory. When 2 of the generated signals exceed the stored values, the SDM will cause current to flow through the inflator modules, deploying the air bags.
The Inflatable Restraint front end discriminating sensor assists the SDM in determining when a deployment should occur by providing an input signal to the SDM.
The IP Module switch is directly interfaced to the Inflatable Restraint Sensing and Diagnostic Module (SDM). The SDM senses the state of the IP module switch. When the switch is in the ON position, the SDM enables possible deployment of the Inflatable Restraint IP module. When the switch is in the OFF position, the SDM disables or inhibits possible deployment of the Inflatable Restraint IP module.