Frontal SIR System

FRONTAL SIR SYSTEM DESCRIPTION

The frontal supplemental inflatable restraint (SIR) system consists of the following components:
- AIR BAG indicator located in the instrument panel cluster (IPC)
- Driver and front passenger knee bolsters
- Inflatable restraint sensing and diagnostic module (SDM)
- Inflatable restraint instrument panel (I/P) module
- Inflatable restraint steering wheel module
- Inflatable restraint steering wheel module coil
- Inflatable restraint seat belt retractor pretensioners
- Inflatable restraint wiring harnesses
- Steering wheel and column

A frontal collision of sufficient force will deploy the frontal air bags and/or pretensioners. The sensing and diagnostic module (SDM) contains a sensing device that converts vehicle velocity changes to an electrical signal. The SDM compares these signals to values stored in memory. If the signals exceed a stored value, the SDM will determine the severity of the impact and either cause current to flow through the frontal deployment loops deploying the frontal air bags and pretensioners, or it will deploy the pretensioners only. The SDM, I/P module, steering wheel module, steering wheel module coil, seat belt retractor pretensioners, 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.