The Air Bag or Supplemental Restraint System (SRS) is designed to provide additional protection for front seat occupants when used in conjunction with a seat belt. The system is an electronically controlled, mechanically operated system. The system contains two basic sub-systems: the air bag module(s) (the actual air bag(s) themselves), and the electrical system. The system consists of:
The system is operates as follows: The system remains out of sight until activated in an accident that is determined to be the equivalent of hitting a parked car of the same size and weight at 28 mph (40 km/h) with the vehicle receiving severe front end damage. This determination is made by crash and safing sensors mounted on the vehicle which when an sufficient impact occurs, close their contacts completing the electrical circuit and inflating the air bags. When not activated the system is monitored by the air bag diagnostic monitor and system readiness is indicated by the lamp located on the instrument cluster. Any fault detected by the diagnostic monitor will illuminate the lamp and store a Diagnostic Trouble Code (DTC).
See Figure 1
When working on the SRS or any components which require the removal of the air bag, adhere to all of these precautions to minimize the risks of personal injury or component damage:
Handling a Live Air Bag Module
See Figures 2 and 3
At no time should any source of electricity be permitted near the inflator on the back of the module. When carrying a live module, the trim cover should be pointed away from the body to minimize injury in the event of accidental deployment. In addition, if the module is placed on a bench or other surface, the plastic trim cover should be face up to minimize movement in case of accidental deployment.
When handling a steering column with an air bag module attached, never place the column on the floor or other surface with the steering wheel or module face down.
Handling a Deployed Air Bag Module
The vehicle interior may contain a very small amount of sodium hydroxide powder, a by-product of air bag deployment. Since this powder can irritate the skin, eyes, nose or throat, be sure to wear safety glasses, rubber gloves and long sleeves during cleanup.
If you find that the cleanup is irritating your skin, run cool water over the affected area. Also, if you experience nasal or throat irritation, exit the vehicle for fresh air until the irritation ceases. If irritation continues, see a physician.
Begin the cleanup by putting tape over the two air bag exhaust vents so that no additional powder will find its way into the vehicle interior. Then, remove the air bag(s) and air bag module(s) from the vehicle.
Use a vacuum cleaner to remove any residual powder from the vehicle interior. Work from the outside in so that you avoid kneeling or sitting in an uncleaned area.
Be sure to vacuum the heater and A/C outlets as well. In fact, it's a good idea to run the blower on low and to vacuum up any powder expelled from the plenum. You may need to vacuum the interior of the car a second time to recover all of the powder.
Check with the local authorities before disposing of the deployed bag and module in your trash.
After an air bag has been deployed, the air bag module and clockspring must be replaced because they cannot be reused. Other air bag system components should be replaced with new ones if damaged.
DISARMING THE SYSTEM
- Position the front wheels straight ahead.
- Place the ignition switch in the LOCK position, then remove the ignition key.
- Disconnect the negative battery cable. Isolate the battery cable by taping up any exposed metal areas of the cable. This will keep the cable from inadvertently contacting the battery and causing accidental deployment of the air bag.
- Allow the system capacitor to discharge for at least 3 minutes, although 10 minutes is recommended to allow the complete dissipation of any residual energy.
ARMING THE SYSTEM
- Turn the ignition switch to the ON position. The SRS indicator lamp should come on for about six seconds and then it will go off.
- Test drive the vehicle and check for an illumination of the SRS indicator lamp.
- Test the horn to ensure that it too works.