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 IP Module
^ Inflatable Restraint IP Module Switch (PSIR)
^ Inflatable Restraint IP Module LED (PSIR)
^ 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 two of the generated signals exceed the stored values, the SDM will cause current to flow through the inflator modules, deploying the air bags.

(PSIR) The SDM is also connected to the inflatable restraint IP module switch and the inflatable restraint IP module LED. The SDM monitors the position of the manual 2-position key in the switch and either disables or enables the inflatable restraint IP module. The SDM provides the ground path for the LED to illuminate if the SDM senses that the inflatable restraint IP module switch has been set to the OFF position. If the inflatable restraint IP module switch has been set to the ON position, the inflatable restraint IP module will be enabled and the ground from the SDM will be removed causing the inflatable restraint IP module LED to extinguish.