The supplemental restraint system (SRS) has been specifically designed to protect the driver and passengers from sustaining severe facial and upper body injuries in the event of a serious impact. Optimum protection can only be achieved when used in conjunction with the conventional three-point safety belts. The safety belts form an integral part of the SRS.
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Passenger air bag module
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Occupant classification sensor
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Side air curtain module
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Safety belt buckle switch 'part of the safety belt buckle and pretensioner'
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 bags and safety belt buckle pretensioners 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) and safety belt buckle pretensioners will deploy only once. In a collision in which they deployed at the first impact, the air bag(s) and safety belt pretensioners will not reduce the risk of injury in a subsequent impact.
In the event of a side impact, in which the side air bags deploy, the front air bags will still deploy in a subsequent front impact, provided that the front impact exceeds the triggering threshold.
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 bags will not deploy. In such circumstances the safety belts would provide sufficient protection for the occupants.
The visible VIN plate, which shows the air bag symbol and either X1, X2 or X4 dependent on the number of air bags fitted, is attached to the windshield edge of the instrument panel.
Vehicles equipped with side air bags can be identified by an embossed AIRBAG logo on the seat fabric adjacent to the air bag module. A label is attached to the B-pillar adjacent to the seat.
WARNING:All vehicles equipped 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 with integral crash sensor
- Front two stage air bag modules
- Side air bag modules
- Side air curtain modules
- Front safety belt buckle and pretensioners (includes a safety belt buckle switch)
- Clockspring
- Crash sensor
- Side impact sensors (vehicle equipped with side air bags)
- Passenger occupant classification sensor
- Driver seat position sensor
- Air bag warning indicator
- Passenger air bag deactivation indicator
Air Bag Control Module
The air bag control module, located under the floor console, governs the operation of the whole system and performs continual system diagnostics. Information on the severity of an impact is received from the crash sensor and, in the event of a side impact, the corresponding side impact sensor.
In the event of a frontal impact, in excess of a predetermined limit, the air bag control module will evaluate the signal received from the front crash sensor against stored data and deploy the front air bag modules and the safety belt buckle pretensioners. However, the safety belt buckles will only deploy if the safety belt buckle is fastened. Variations in the deployment of the front air bag modules are dependent on the status of the driver seat position, passenger occupant classification sensor and the front safety belt buckles.
In the event of a side impact, in excess of a predetermined limit, the air bag control module will evaluate the signal received from either of the side impact sensors against stored data and deploy the corresponding side air bag module and, if equipped, the side air curtain module.
On vehicles equipped with the telematics system there is an interface with the telematics control module. In the event of an air bag deployment the telematics control module will automatically send a SOS signal.
In the event of a failure in the vehicle power supply during an accident, the air bag control module provides an auxiliary power supply, sufficient to deploy the air bag(s) for a minimum of 150 mS. The vehicle battery supply maintains the air bag control module auxiliary supply and supports all other SRS functions when the ignition is in the 'RUN' position. In the event of a fault being detected by the air bag control module the air bag warning indicator is illuminated. The behavior of the warning indicator depends on the type of fault present.
The air bag control module can be reset, using WDS, and used for up to five collisions in which the air bags deployed.
Front Two Stage Air Bag Modules.
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Passenger air bag module first stage electrical connection (black electrical connector)
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Passenger air bag module second stage electrical connector (brown electrical connector)
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' molded in its surface allowing the air bag to easily exit through the cover when the system deploys. The driver air bag has a volume of 55 liters.
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 located above the glove compartment and is secured to the cross-vehicle beam and the instrument panel. The passenger air bag cover is an integral part of the instrument panel which has invisible 'split lines' to allow the passenger air bag to easily exit when the system deploys. The passenger air bag has a volume of 110 liters.
A new passenger air bag module and wiring harness with the air bag module electrical connectors must be installed following deployment.
Both the driver and passenger air bag modules contain two inflators. In the event of a frontal impact, in excess of a predetermined limit, the air bag control module will deploy the driver first stage inflator followed by the second stage inflator. The lapse time between the deployment of the first stage inflator and the second stage inflator is directly related to the accident severity and the information received by the air bag control module from the driver seat position sensor.
The air bag control module will also deploy the passenger air bag first stage inflator, provided that the passenger occupant classification sensor senses that the seat is occupied. The passenger second stage inflator will then also deploy and the lapse time between the first stage inflator deployment and the second stage inflator deployment is directly related to accident severity.
Regardless of the driver seat position or the passenger occupant classification sensor (unless the occupant classification sensor determines that the passenger seat is unoccupied) both the second stage inflators will deploy 100 mS following the first stage deployment. This 'disposal' deployment has no effect on the air bag pressure, but is a protection measure for the rescue services.
Side Air Bag Modules
The side air bag will deploy on the same side that the air bag control module received the signal from the side impact sensor. The side air bag modules, if equipped, are integrated into the front seat backrests providing an unobtrusive appearance. The unique seat cover has been designed to accommodate air bag deployment. When the side air bag is deployed the stitched seam of the seat cover adjacent to the side air bag module splits, allowing the air bag to exit the seat backrest unobstructed. Each side air bag has a volume of 11 liters.
Side Air Curtain Modules
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Folded side air curtain module
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Side air curtain module electrical connection
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Side air curtain module retaining bolt
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Side air curtain module inflator
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Folded side air curtain
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Side air curtain rear retaining cord
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Unfolded side air curtain
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Side air curtain front retaining cord
The side air curtain modules are located under the headliner between the A and C-pillar and deployed at the same time as the corresponding side air bag. If the passenger air bag is deactivated the corresponding side air bag is also deactivated, however the side air curtain will still deploy to afford protection to any corresponding rear occupant. When deployed, the side air curtain extends down to approximately shoulder height to protect both the front and rear occupants heads. Both the front and rear of the side air curtain are retained to the A and C-pillar respectively by cords.
The side air curtain inflator generates the gas needed to fill the side air curtain. It consists of a high strength steel casing filled with a solid propellant charge, an electrically activated ignitor and a cold gas bottle with pressurized gas. The ignitor is activated by a signal from the air bag control module, which ignites the propellant. The burning propellant opens the membrane of the cold gas bottle and heats the pressurized gas. The expanding gas is directed by the seal into the gas tube and emits through holes in the tube to the front and rear side air curtain chambers. The force of the occupant's heads on the side air curtain forces the gas from the front and rear chambers into an overflow chamber, thus producing a dampening effect. Each side air curtain has an approximate volume of 24 liters.
A new side air curtain module and wiring harness with the air curtain module electrical connectors must be installed following deployment.
Front Safety Belt Buckle and Pretensioners
The front safety belt buckles and pretensioners are seat mounted and incorporate a safety belt buckle switch. In the event of a front or side impact the air bag control module will deploy the pretensioners provided the safety belt buckles are fastened. The safety belt buckle pretensioners have a lower deployment threshold than that required by the air bags. Hence it is possible during a minor collision, which exceeds the deployment threshold, that only the safety belt pretensioners will deploy. The air bag control module receives information on the status of the safety belt buckles from a switch contained in the buckle.
For additional information, refer to: Safety Belt System - Vehicles Built Up To: 06/2003 (501-20A Safety Belt System, Description and Operation) /
Safety Belt System - Vehicles Built From: 06/2003 (501-20A Safety Belt System, Description and Operation).
A new safety belt buckle and pretensioner must be installed following deployment.
Air Bag and Safety Belt Pretensioners Deployment Logic
The driver and front passenger air bags have different deployment thresholds for when the safety belt buckle is fastened or unfastened. If the driver or front passenger safety belt buckle is unfastened the respective air bag deployment threshold will be lower than a fastened safety belt buckle deployment threshold.
With the driver seat in the forward position and the driver safety belt buckle fastened, the driver air bag will be deployed at the driver safety belt buckle unfastened threshold.
Depending on which front safety belt buckle(s) are fastened and the severity of the impact, there are scenarios where it is possible that only one of the two front air bags will be deployed. For example: The driver safety belt buckle unfastened, passenger safety belt buckle fastened and the impact has reached the unfastened threshold. The driver air bag will deploy but the driver safety belt pretensioner will not deploy, passenger air bag will not deploy but the passenger safety belt pretensioner will deploy.
The clockspring is designed to carry signals between the air bag control module and the driver air bag module. The clockspring 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.
It is advisable to install a new clockspring following a driver air bag deployment.
The front crash sensor is located under the radiator grille opening panel to facilitate impact sensing along the longitudinal axis. The air bag control module processes the crash data sent by the front crash sensor against stored data, and deploys the front air bags.
The crash sensor can be reused following external examination and system self-test.
The side impact sensors are mounted at the base of the B-pillars to facilitate lateral impact sensing. In the event of a side impact, the air bag control module processes the crash data sent by the side impact sensor against stored data. The air bag control module will deploy the side air bag, both safety belt buckle pretensioners and, if equipped, the side air curtain on the side the deployment request was initiated.
The side impact sensors can be reused following external examination and system self-test.
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Occupant classification sensor mat
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Seat sensors 'part of the occupant classification sensor mat'
The passenger occupant classification sensor consists of the following components:
- Sensor mat with integrated pressure sensors
- Electronic control unit
- Wiring harness
The occupant classification sensor detects, by integrated pressure sensors, the presence of a passenger or object on the seat cushion. The occupant classification sensor cannot discriminate between a passenger and an object. The electronic control unit processes the pressure information and, if the pressure exceeds a threshold, an 'Occupied Seat' state is communicated through the wiring harness to the air bag control module. If the seat is empty or occupied by a very light object an 'Empty Seat' state is transmitted to the air bag control module and the passenger air bag will be deactivated to avoid unnecessary repair costs. If the seat is empty and the safety belt is buckled the passenger air bag deactivation indicator will be illuminated.
The occupant classification sensor system is not affected by the position of the passenger seat.
The electronic control unit monitors the occupant classification sensor and if a fault is detected will communicate the fault to the air bag control module through the corporate area network (CAN) and illuminate the air bag warning light.
Seat Position Sensor
