SIR System Description

SIR SYSTEM DESCRIPTION

The SIR system consists of the following components:
- AIR BAG indicator located in the instrument panel cluster (IPC)
- Driver and passenger knee bolsters
- Inflatable restraint front end discriminating sensor
- 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 air bags. The SDM contains a sensing device (accelerometer) that converts vehicle velocity changes to an electrical signal. In the event of a frontal collision, the SDM receives a signal from the front end discriminating sensor which assists the SDM in determining the severity of some frontal collisions. The SDM contains a microprocessor that performs calculations using the measured accelerations. The SDM 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 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 diagnostic trouble code (DTC) and turns the AIR BAG indicator ON. The SDM, IP module, steering wheel module, steering wheel module coil and the connecting wires makeup the deployment loops. The SDM continuously monitors the deployment loops for malfunctions and turns the AIR BAG indicator ON if a fault is detected.