Air Bag Module
Caution: Refer to SIR Caution in the Preface section.
Driver Air Bag Module
The driver air bag module is under the center pad on the steering wheel.
The driver air bag module contains an ignitor charge and a gas generator to inflate the folded air bag.
Passenger Air Bag Module
The passenger air bag module is on the passenger side of the instrument panel.
The passenger air bag module contains an ignitor charge and a gas generator to inflate the folded air bag.
Sensing and Diagnostic Module (SDM)
The SDM
| • | Has no user-serviceable parts |
| • | Is under the front console assembly |
| • | Continuously monitors the system components |
| • | Records any faults which are discovered |
| • | Illuminates a warning lamp that alerts the driver to any faults |
| • | Allows the fault codes to be retrieved with a scan tool |
The SDM controls the deployment of the air bag system through the use of the following:
| • | Arming sensor |
| • | Capacitor |
| • | Crash sensor, or accelerometer |
Arming Sensor
The arming sensor is safety device made up of a dual-contact, electro-mechanical switch that:
| • | Acts independently of the electronic components |
| • | Keeps the firing circuits for the air bags unarmed under normal driving conditions |
| • | Allows the air bags to deploy under the required conditions |
Capacitor
The capacitor provides reserve power.
Crash Sensor
The crash sensor, or accelerometer, electronically represents the acceleration or deceleration of the vehicle during a frontal impact. In this electronic representation, the electrical signal is proportional to the acceleration or deceleration of the vehicle.
SIR Warning Lamp
The supplemental inflatable restraints (SIR) system includes a self-diagnostic function.
If there is a failure of the sensing and diagnostic module or the external circuits, the SIR warning lamp in the instrument cluster turns ON.
As a system check, the SIR warning lamp also turns ON when the ignition is first switched to the ON position.
Correct Functioning
The system is working properly if the SIR warning lamp turns OFF after approximately 4 seconds.
Faulty Functioning
The system is not working properly, meaning one of the SIR components or the wiring connector is faulty, if:
| • | The SIR warning lamp fails to turn ON when the ignition is first switched ON. |
| • | The SIR warning lamp remains ON. |
Coil Spring
The coil spring:
| • | Is on the steering column |
| • | Contains a coil that is the electrical contact between the steering column wiring harness and the driver side air bag module |
| • | Is part of the circuit for the horn |
Notice: Do not rotate the steering wheel or move the position of the steering gear once the intermediate shaft is disconnected. This will uncenter the Inflatable Restraint coil in the steering column. If the Inflatable Restraint coil becomes uncentered, it may be damaged during vehicle operation.
Turning the steering wheel:
| • | In one direction tightens the coil |
| • | In the opposite direction loosens the coil |
| • | More than 3 ¼ turns may damage the coil spring |
Caution: Coil Spring Disassembly can cause personal injury and vehicle damage.
The coil spring should never be disassembled.
The coil spring must be replaced if the air bags have been deployed.
Wiring Harness/Connectors
The connector for the sensing and diagnostic module (SDM) has a built-in shorting bar that will turn ON the warning lamp if there is a poor connection at the SDM.
As an anti-deployment mechanism, additional shorting bars are in the following:
| • | Connector for the coil spring at the lower steering column |
| • | Passenger air bag module connector |
| • | SDM connector |
When these connectors are separated, the shorting bars will short circuit any current which is applied, preventing the current from reaching the air bag modules.
SIR System
The supplemental inflatable restraints (SIR) system is a safety device used in conjunction with the seat belts.
The air bag does not replace the function of the seat belt. The driver and the passengers must always fasten their seat belts and adjust them for a proper fit.
The SIR is designed to protect the driver and the front seat passenger in the event of a significant frontal impact to the vehicle. The air bags deploy if the force is applied from a direction within 30 degrees of the vehicle's centerline and above 25 km/h (15 mph) speed.
The SIR consists of the following:
| • | Driver air bag module |
| • | Passenger air bag module |
| • | Sensing and diagnostic module |
| • | Steering column coil spring |
| • | Wiring harness |
| • | SIR malfunction warning lamp |
General Precautions
The supplemental inflatable restraints (SIR) warning lamp must illuminate when the ignition is switched ON, and then turn OFF after approximately 4 seconds.
There is a fault in the air bag system if the following conditions occur:
| • | The warning lamp does not turn OFF. |
| • | The warning lamp illuminates while the vehicle is in operation. |
If the warning lamp indicates there is a fault in the air bag system, assume that the SIR system may not be functional.
Caution: Refer to SIR Inflatable Module Deployment Outside Vehicle Caution in the Preface section.
Caution: Refer to SIR Caution in the Preface section.
Caution: Refer to SIR Deployed Inflator Modules Are Hot Caution in the Preface section.
Caution: Refer to SIR Inflator Module Coil Caution in the Preface section.
Caution: Refer to SIR Inflatable Module Deployment Outside Vehicle Caution in the Preface section.
Caution: Refer to SIR Inflator Module Disposal Caution in the Preface section.
Caution: Refer to SIR Inflator Module Handling and Storage Caution in the Preface section.
Caution: Refer to SIR Special Tool Caution in the Preface section.
Only trained personnel at franchised General Motors dealers and authorized General Motors service dealerships may service the air bag system.
Never attempt to disassemble, repair, or reuse the following:
| • | Air bag modules |
| • | Coil spring |
| • | Sensing and diagnostic module |
| • | Wiring harness |
When making SIR repairs,
| • | Inspect any SIR part before it is installed. |
| • | Use only new parts. |
| • | Do not install used SIR parts from other vehicles. |
| • | Do not install any part that has been dropped or that has dents, cracks, or other defects. |
Air Bag Deployment Condition
The air bag is designed to deploy under 30 degrees left/right angle barrier and above 25 km/h (15 mph) speed.
Concrete Barrier Deployment Condition
In case of the 0 degrees frontal concrete barrier, air bag may deploy above 25 km/h (15 mph) speed.
Air Bag Deployment Procedure
- Non-Deployment condition
- When crashing, firing current flows from the SDM to the initiator.
- The initiator is burning and the inside pressure is increasing and the piston hits the safety disc.
- The safety disc is broken and the compressed AR gas is spouted out.
- Compressed AR gas and the burned initiator are carburated, and the air bag is deployed.
| • | Initiator (4) |
| • | Piston (1) |
| • | Safety disc (3) |
| • | Compressed AR gas (2) |
