SIR System

SIR SYSTEM OVERVIEW

SIR System Overview:

The Supplemental Inflatable Restraint (SIR) system supplements the protection offered by the occupant's seat belt system (2). The SIR system may contain several inflator modules located throughout the vehicle, i.e. steering wheel module (1), Instrument Panel (IP) module (1). Each inflator module has a deployment loop that is controlled by the Sensing And Diagnostic Module (SDM) mounted inside the vehicle. The SDM determines the severity of a collision with the assistance of various sensor inputs. When the SDM detects a collision of sufficient force it will process the information provided by the sensors to further support air bag deployment. The SDM performs continuous diagnostic monitoring of the SIR system electrical components. Upon detection of a circuit malfunction, the SDM will set a Diagnostic Trouble Code (DTC) and inform the driver by turning the AIR BAG indicator ON. The steering column and knee bolsters (3) are designed to absorb energy and compress during frontal collisions in order to limit leg movement and decrease the chance of injury to the driver and passenger.

FRONTAL SIR SYSTEM DESCRIPTION
The frontal SIR system consists of the following components:
^ AIR BAG indicator located in the Instrument Panel Cluster (IPC)
^ Driver and passenger knee bolsters
^ Inflatable restraint IP module
^ Inflatable restraint Sensing And Diagnostic Module (SDM)
^ Inflatable restraint steering wheel module
^ Inflatable restraint steering wheel module coil
^ Inflatable restraint wiring harnesses
^ Steering wheel and column

A frontal collision of sufficient force will deploy the frontal air bags. The SDM contains a sensing device that converts vehicle velocity changes to an electrical signal. The SDM also contains a microprocessor that performs calculations using the measured accelerations and compares these calculations to a value stored in memory. When the generated calculations exceed the stored value, the SDM will cause current to flow through the frontal deployment loops deploying the frontal air bags. Once the air bags are inflated they quickly deflate through the air bag vent holes. After the air bags have deployed, the SDM sets a DTC and turns the AIR BAG indicator ON. The SDM, IP module, steering wheel module, steering wheel module coil, and the connecting wires make up the frontal deployment loops. The SDM continuously monitors the deployment loops for malfunctions and turns the AIR BAG indicator ON if a fault is detected.