SIR System

Frontal Restraint Devices
The frontal Supplemental Inflatable Restraint (SIR) system supplements the protection offered by the driver and front passenger seat belts. The frontal SIR system deploys an air bag from the center of the steering wheel and from the right side of the instrument panel.

The seat belt pretensioners remove slack from the driver and passenger front seat belts during a frontal impact. The frontal SIR system deploys the seat belt pretensioners with the frontal air bags.







Frontal SIR System Description
A frontal crash of sufficient force up to 30 degrees off the longitudinal centerline of the vehicle will deploy the frontal air bags and the pretensioners. The knee bolsters absorb crash energy. The driver and passenger knee bolsters are below the instrument panel.
The frontal 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 Side Impact Module - Left
^ Inflatable Restraint Side Impact Module - Right
^ Seat Belt Pretensioner - LF
^ Seat Belt Pretensioner - RF
^ Inflatable Restraint Side Impact Sensors
^ AIR BAG Indicator in the Instrument Panel Cluster

The Inflatable Restraint Sensing And Diagnostic Module (SDM), inflatable restraint steering wheel module coil, inflatable restraint steering wheel module, inflatable restraint IP module, seat belt pretensioner - LF, seat belt pretensioner RF, 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 to cause deployment 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 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 allow current to flow through the frontal inflator modules and the pretensioners causing deployment.







Side Impact Restraint Devices
The side impact air bag system supplements the protection offered by the driver door, the front passenger door, and the vehicle structure. The side impact air bag system deploys an air bag from the side of the driver or front passenger seat. A side crash of sufficient force will deploy a side air bag.

Side Impact Air Bag System Description
The side impact air bag system consists of the following components:
^ 2 Inflatable Restraint Side Impact Sensors (SIS) (1 in each B-pillar)
^ An Inflatable Restraint Side Impact Module - Left in the driver's seat
^ An Inflatable Restraint Side Impact Module - Right in the front passenger's seat
^ An AIR BAG Indicator in the Instrument Panel Cluster
^ An Inflatable Restraint Sensing and Diagnostic Module (SDM)

The Inflatable Restraint Side Impact Sensor (SIS), the inflatable restraint side impact modules, and the connecting wires make up the side impact deployment loops. The function of the side impact deployment loop is to supply current through the side impact inflator module, which will cause deployment of the side impact air bag. Deployment occurs when one of the SIS's detects a side impact severe enough to warrant deployment.

The SIS contains a sensing device (accelerometer) that converts acceleration into an electrical (analog) signal. This signal is converted by a microprocessor in the SIS into acceleration and velocity data. This data is used by a sensing algorithm and compared to various predetermined boundary conditions. When the acceleration value exceeds the predetermined threshold, and the velocity boundary is crossed, the SIS will cause current to flow through the inflatable restraint side impact module - left or the inflatable restraint side impact module - right.