Restraints and Safety Systems: Description and Operation

Supplemental Restraint System:

An occupant restraint system is standard factory-installed safety equipment on this model. Available occupant restraints for this model include both active and passive types. Active restraints are those which require the vehicle occupants to take some action to employ, such as fastening a seat belt; while passive restraints require no action by the vehicle occupants to be employed.

ACTIVE RESTRAINTS
The active restraints for this model include:
- Front Seat Belts - Both outboard front seating positions are equipped with three-point seat belt systems employing a lower B-pillar mounted inertia latch-type retractors, height-adjustable upper B-pillar mounted turning loops, travelling lower seat belt anchors secured to the outboard seat tracks, and travelling end-release seat belt buckles secured to the inboard seat track. The driver side front seat belt buckle of all models includes an integral seat belt switch that detects whether its seat belt has been fastened.
- Rear Seat Belts - All rear seating positions are equipped with three-point seat belt systems. Each rear seating position belt employs an integral seat cushion frame mounted inertia latch-type retractor, a fixed position upper seat back frame mounted turning loop, and a fixed lower seat belt anchor secured to the seat cushion frame. All rear seat belts have fixed end-release seat belt buckles that are also secured to the seat cushion frame.

PASSIVE RESTRAINTS

SRS Logo:

A Next Generation driver airbag is standard factory-installed safety equipment on this model, while a passenger side front airbag is optional. This airbag system is a passive, inflatable, Supplemental Restraint System (SRS) and vehicles with this equipment can be readily identified by the "SRS - AIR-BAG" logo molded into the driver airbag trim cover in the center of the steering wheel and, if the vehicle is so equipped, also into the passenger airbag door on the instrument panel above the glove box. Vehicles with the airbag system can also be identified by the airbag indicator, which will illuminate in the instrument cluster for about six seconds as a bulb test each time the ignition switch is turned to the On position. A pyrotechnic-type seat belt tensioner is integral to the front seat belt retractor mounted on the lower B-pillar on the driver side, and to the passenger side retractor of vehicles equipped with the optional passenger side airbag.

The supplemental restraint system includes the following major components, which are described in further detail elsewhere in this service information:
- Airbag Control Module - The Airbag Control Module (ACM) is located on a mount on the floor panel within the driver side seat riser, beneath the driver seat in the passenger compartment.
- Airbag (SRS) Indicator - The airbag indicator is integral to the ElectroMechanical Instrument Cluster (EMIC), which is located on the instrument panel in front of the driver.
- Clockspring - The clockspring is located near the top of the steering column, directly beneath the steering wheel.
- Driver Airbag - The driver airbag is located in the center of the steering wheel, beneath the driver airbag trim cover.
- Driver Knee Blocker - The structure of the lower instrument panel serves as a knee blocker for the driver.
- Passenger Airbag - The optional passenger air-bag is located within the instrument panel, behind the passenger airbag door on the instrument panel above the glove box on the passenger side of the vehicle.
- Passenger Knee Blocker - The structure of the glove box door and the lower instrument panel serve as a knee blocker for the front seat passenger.
- Seat Belt Tensioner - A seat belt tensioner is integral to the driver side front seat belt retractor unit, and to the passenger side front seat belt retractor unit on vehicles equipped with an optional passenger airbag.

The ACM contains a central processing unit and programming that allows it to communicate on a serial data bus diagnostic circuit connected to the 16-way Data Link Connector (DLC) located below the left end of the instrument panel. This method of communication is used for initialization of the ACM and for diagnosis of the SRS circuits and components using a DRBIII(R) scan tool.

Hard wired circuitry connects the supplemental restraint system components to each other through the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system, and to the supplemental restraint system components through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

ACTIVE RESTRAINTS
The primary passenger restraints in this or any other vehicle are the standard equipment factory-installed seat belts. Seat belts are referred to as an active restraint because the vehicle occupants are required to physically fasten and properly adjust these restraints in order to benefit from them. See the owner's manual in the vehicle glove box for more information on the features, use and operation of all of the factory-installed active restraints.

PASSIVE RESTRAINTS
The passive restraints are referred to as a supplemental restraint system because they were designed and are intended to enhance the protection for the occupants of the vehicle only when used in conjunction with the seat belts. They are referred to as passive restraints because the vehicle occupants are not required to do anything to make them operate; however, the vehicle occupants must be wearing their seat belts in order to obtain the maximum safety benefit from the factory-installed supplemental restraint system.

The supplemental restraint system electrical circuits are continuously monitored and controlled by a microprocessor and software contained within the Airbag Control Module (ACM). An airbag indicator in the ElectroMechanical Instrument Cluster (EMIC) illuminates for about four seconds as a bulb test each time the ignition switch is turned to the On or Start positions. Following the bulb test, the airbag indicator is turned on or off by the ACM to indicate the status of the supplemental restraint system. If the airbag indicator comes on either solid or flashing at any time other than during the bulb test, it indicates that there is a problem in the supplemental restraint system electrical circuits. Such a problem may cause airbags not to deploy when required, or to deploy when not required.

Deployment of the supplemental restraints depends upon the angle and severity of an impact. Deployment is not based upon vehicle speed; rather, deployment is based upon the rate of deceleration as measured by the forces of gravity (G force) upon the impact sensor. When an impact is severe enough, the microprocessor in the ACM signals the inflator of the appropriate airbag units to deploy their airbag cushions. The front seat belt tensioners are provided with a deployment signal by the ACM in conjunction with the driver and passenger airbags. During a frontal vehicle impact, the knee blockers work in concert with properly fastened and adjusted seat belts to restrain both the driver and the front seat passenger in the proper position for an airbag deployment. The knee blockers also absorb and distribute the crash energy from the driver and the front seat passenger to the structure of the instrument panel. The seat belt tensioners remove the slack from the front seat belts to provide further assurance that the driver and front seat passenger are properly positioned and restrained for an airbag deployment.

Typically, the vehicle occupants recall more about the events preceding and following a collision than they do of an airbag deployment itself. This is because the airbag deployment and deflation occur so rapidly. In a typical 48 kilometer-per-hour (30 mile-per-hour) barrier impact, from the moment of impact until the airbags are fully inflated takes only a few milliseconds. Within one to two seconds from the moment of impact, the airbags are almost entirely deflated. The times cited for these events are approximations, which apply only to a barrier impact at the given speed. Actual times will vary somewhat, depending upon the vehicle speed, impact angle, severity of the impact, and the type of collision.

When the ACM monitors a problem in any of the front airbag system circuits or components, including the seat belt tensioners, it stores a fault code or Diagnostic Trouble Code (DTC) in its memory circuit and sends a hard wired output to the EMIC to turn on the airbag indicator. If the EMIC detects a problem in the airbag indicator or airbag indicator circuit, the cluster will flash the seatbelt indicator on and off. Proper testing of the supplemental restraint system components as well as the retrieval or erasure of a DTC from the ACM requires the use of a DRBIII(R) scan tool. Refer to the appropriate diagnostic information.

See the owner's manual in the vehicle glove box for more information on the features, use and operation of all of the factory-installed passive restraints.