Frontal SIR System Description

The frontal SIR system consists of the following components:
1. Inflatable restraint sensing and diagnostic and Seat Belt Pretensioner Module (SDM)
2. Inflatable restraint steering wheel module
3. Inflatable restraint steering wheel module coil
4. Inflatable restraint IP module
5. Driver seat belt pretensioner
6. Passenger seat belt pretensioner
7. The AIR BAG Warning Lamp in the Instrument Panel Cluster (IPC)

The inflatable restraint sensing and diagnostic and Seat Belt Pretensioner Module (SDM), inflatable restraint steering wheel module coil, inflatable restraint steering wheel module, inflatable restraint IP module, driver seat belt pretensioner, passenger seat belt pretensioner, and the connecting wires make up the frontal deployment loops. The function of the frontal deployment loops is to supply current through the frontal inflator modules and the pretensioners, deploying the seat belt pretensioners, in the event of a mild frontal collision, and deploying the frontal inflator modules and the pretensioners in the event of a mild-to-severe frontal collision. Deployment occurs when the SDM detects vehicle velocity changes severe enough to warrant deployment. The seat belt pretensioners fire first, removing any slack in the driver and front passenger shoulder belts.

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 frontal inflator modules and the pretensioners, deploying the frontal inflator modules and the pretensioners.