The supplemental restraint system (SRS) is designed to protect the driver and front seat outer passenger (when equipped with a passenger air bag) from sustaining severe facial and upper body injuries in the event of a serious impact, when used in conjunction with the conventional two-point and three-point safety belt system. The safety belts form an integral part of the SRS.
The SRS is designed to deploy only in the event of a collision, with the ignition in the RUN position.
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Air bag sliding contact
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Passenger air bag module
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Air bag warning indicator
The driver, wearing the safety belt provided, should position the seat as far back as is practical, so the steering wheel can be reached with arms slightly angled, thereby leaving a gap between the steering wheel and the driver.
The passenger, wearing the safety belt provided, should not position himself or herself so that the air bag cover is in direct contact with the occupants’ body.
The front air bag(s) will deploy in the event of a direct front impact or when the impact angle is up to 30 degrees from the left or right of the vehicle center line.
The air bag(s) will deploy only once. In a collision in which they deployed at the first impact, the air bag(s) will not reduce the risk of injury in a subsequent impact.
Under certain circumstances, although the damage sustained by the vehicle may look extensive, the impact may remain below the triggering threshold of the SRS and the air bag(s) will not deploy. In such circumstances the safety belts would provide sufficient protection for the occupants.
The visible vehicle identification number (VIN) plate, which shows the air bag symbol and either X1 or X2 dependent on the number of air bags fitted, is attached to the windshield edge of the instrument panel.
WARNING:All vehicles fitted with the passenger air bag from the factory have a WARNING sticker attached to the instrument panel, PROHIBITING the use of rear facing child or baby seats.
The SRS consists of the following components:
- air bag control module
- wiring harness
- air bag sliding contact
- warning indicator
- air bag module(s)
The air bag control module governs the operation of the whole system, including the diagnostic element. It contains two frontal impact micro machine sensors; a crash sensor and a safing sensor. These two sensors are connected in series and if they both sense a deceleration in excess of a predetermined limit, the air bag control module will deploy the air bag module(s).
The air bag control module also performs continual system diagnostics. In the event of a fault being detected the warning indicator is illuminated either constantly or intermittently. The behavior of the warning indicator depends on the type of fault present. The warning indicator is located in the instrument cluster.
The air bag control module can be reset, using WDS, and used for up to five collisions in which the air bags deployed.
The wiring harness provides power to the air bag control module from the vehicle supply and hence to the air bag module(s).
The air bag sliding contact is designed to carry signals between the air bag control module and the driver air bag module. The air bag sliding contact is fitted to the steering column, and consists of fixed and moving parts connected by a coiled Mylar tape with integral conducting tracks. The Mylar tape is able to "wind up" and "unwind" as the steering wheel (to which the moving part is attached) is turned, maintaining electrical contact at all times between the air bag control module and the driver air bag module. The air bag sliding contact is used in order to achieve the high degree of circuit integrity required by such a critical safety system as the SRS.
A new air bag sliding contact must be installed following a driver air bag deployment.
The driver and passenger air bag modules consist of the following components which cannot be disassembled:
- inflator
- air bag
- container
- cover
The inflator is screwed into a plastic container. The air bag is then folded on top of the inflator and the whole subassembly is enclosed by the cover.
The driver air bag module is fitted to the steering wheel, the cover forming the outer surface of the steering wheel boss. The cover has invisible "split lines" moulded in its surfaces allowing the air bag to easily exit through the cover when the system deploys.
A new driver air bag module and wiring harness with the air bag module electrical connectors must be installed following deployment.
The passenger air bag module is integrated into the front of the instrument panel to provide an unobtrusive appearance. The cover incorporates an invisible "split line" moulded in its surface along the lower edge and hinged along the upper edge. As the air bag deploys, the lower edge of the cover splits allowing the air bag to easily exit. The cover remains secured to the air bag module body by the hinge.
A new passenger air bag module and wiring harness with the air bag module electrical connectors must be installed following deployment.
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Passenger air bag module wiring harness
Vehicles without a passenger air bag module have a bridge resistor fitted to the passenger air bag wiring harness in place of the passenger air bag module.
The purpose of the inflator is to generate the gas needed to fill the air bag. It consists of a high strength steel casing filled with a solid propellant charge and an electrically activated igniter. The igniter is activated by a signal from the air bag control module which in turn ignites the propellant charge. The very rapid burning of the propellant produces sufficient gas to fill the air bag(s). As the gases expand they cool, preventing heat damage to the bag. The drivers air bag module has one inflator and bag, with a filled volume of 57 liters. The passenger air bag module has one inflator and bag having a filled volume of 57 liters.
The air bag(s) are a one-piece woven item with a silicon coating to provide flame and heat protection in the vicinity of the inflator. The shape of the passenger air bag is tailored to the vehicle proportions. In order to prevent the folds of the air bag from sticking together in its tightly stowed position, the fabric may be treated with talcum powder. When the air bag(s) deploy, some of the fine powder is blown into the vehicle. This powder is visible as a dust cloud and also has a characteristic odor. The particles soon settle and do not represent a health risk. The dust cloud is not a sign of external combustion outside the air bag inflator cartridge.
When the air bag(s) deploy, they remain fully inflated for only a fraction of a second and start to deflate immediately, cushioning the occupant. The high speed of inflation along with the surrounding events and noise from the impact can give the impression that the air bag(s) did not deploy to their full extent.
In certain circumstance slight grazing or minor friction burns can result from air bag deployment.
There are two processes which are involved:
- Friction can occur between the fabric of the air bag and unprotected areas of the skin, either during its very rapid deployment or when the occupant contacts the air bag.
- Hot gases from the charge used to inflate the air bag vent as it starts to deflate. Depending on the position of the drivers hands, or how close the occupant is to the air bag, it is not always possible to exclude the possibility of these gases contacting areas of the skin unprotected by clothing.
The SRS will communicate concerns during a driving cycle or after initial key ON by means of a warning indicator located in the instrument cluster.
