Driver's side and passenger air bags are standard equipment on all models covered by this guide. The Supplemental Inflatable Restraint (SIR) system offers protection in addition to that provided by the seat belt by deploying an air bag from the center of the steering wheel or dash panel. The air bag deploys when the vehicle is involved in a frontal crash of sufficient force up to 30° off the centerline of the vehicle. To further absorb the crash energy, there is also a knee bolster located beneath the instrument panel in the driver's area and the steering wheel is collapsible.
The SIR deployment loop consists of the following components:
The Sensing and Diagnostic Module (SDM), inflatable restraint steering wheel module coil (SIR coil assembly), inflatable restraint steering wheel module (driver inflator module), inflatable restraint instrument panel module (passenger inflator module), and connector wires make up the deployment loops. The function of the deployment loops is to supply current through the inflator modules, which will cause deployment of the air bags.
Deployment occurs when the SDM detects 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 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 these generated signals exceed the stored values, the SDM will cause current to flow through the inflator modules, deploying the air bags.
The Sensing and Diagnostic Module (SDM) performs the following functions in the SIR system:
The SDM connects to the SIR wiring harness using a 12-way connector. The SDM harness connector uses shorting bar across certain terminals in the contact area. Removal of the SDM Connector Position Assurance (CPA) or harness connector itself will connect the AIR BAG warning lamp to ground through the shorting bar. The CPA is a small wedge-shaped plastic piece designed to lock the connector together.
The AIR BAG warning lamp will come ON steady with power applied to the SDM when either one of the following two conditions exist:
The SDM receives power whenever the ignition switch is in the RUN or START positions.AIR BAG Warning Lamp
The AIR BAG warning lamp is the key to driver notification of SIR system malfunctions.
The ignition switch applies ignition voltage to the AIR BAG warning lamp. The AIR BAG warning lamp receives power whenever the ignition switch is in the RUN or START positions. The SDM controls the lamp by providing ground with a lamp driver. The SIR system uses the AIR BAG warning lamp to do the following:
SIR Coil Assembly
The SIR steering wheel module coil assembly consists of two or more current carrying coils. They are attached to the steering column and allow rotation of the steering wheel while maintaining continuous deployment loop contact through the inflator module.
There is a shorting bar on the yellow 2-way connector near the base of the steering column that connects the steering wheel module coil to the SIR wiring harness. The shorting bar shorts the circuit when the connector is disengaged. The circuit to the inflator module is shorted in this way to prevent unwanted air bag deployment when servicing the steering column or other SIR components.Inflator Module
The inflator module consists of an inflatable bag and an inflator (a canister of gas-generating material and an initiating device). When the vehicle is in a frontal crash of sufficient force to close the arming sensor and at least one discriminating sensor simultaneously, current flows through the deployment loop. Current passing through the initiator ignites the material in the inflator module, causing a reaction which produces a gas that rapidly inflates the air bag.
All vehicles are equipped with a driver's side inflator module located in the steering wheel and a passenger side inflator module located in the dash panel.Steering Column
The steering column is energy absorbing. The steering column can compress during a frontal crash in order to decrease the chance of injury to the driver.Knee Bolster
The knee bolsters absorb energy and control the forward movement of the vehicle's front occupants during a frontal crash by limiting leg movement.
DISABLING THE SYSTEM
- Turn the steering wheel so that the vehicle's wheels are pointing straight ahead.
- Turn the ignition switch to LOCK , remove the key, then disconnect the negative battery cable.
- Remove the "AIR BAG" fuse from the instrument panel left end (driver's) fuse box.
- Remove the Connector Position Assurance (CPA) from the yellow two way connector located above the driver's fuse box. The CPA is a small wedge-shaped plastic piece designed to lock the connector together. Disconnect the yellow two way connector (1)
- Repeat steps 3 and 4 for the fuse box at the right end (passenger side) of the instrument panel.
- Connect the negative battery cable.
ENABLING THE SYSTEM
- Turn the ignition switch to LOCK , then remove the key.
- Disconnect the negative battery cable.
- Connect the yellow 2-way connector located above the driver's side fuse box.
- Install the Connector Position Assurance (CPA) to the yellow 2-way connector located above the driver's fuse box.
- Repeat steps 3 and 4 for the passenger side fuse box.
- Install the "AIR BAG" fuse to the driver's fuse block.
- Connect the negative battery cable.
- Turn the ignition switch to RUN and make sure that the "AIR BAG" warning lamp flashes seven times and then shuts off. If the warning lamp does not shut off, make sure that the wiring is properly connected. If the light remains on, take the vehicle to a reputable repair facility for service.