Air Bag Systems

Contour Shown, Mystique Similar:

These vehicles have a single point sensing system. The diagnostic monitor, crash sensors and safing sensor are incorporated into an electronic air bag control module mounted centrally in the vehicle. The air bag control module retains full control of the complete air bag system.

The Supplementary Restraint System (SRS) has been specifically designed to protect the driver and passenger from sustaining severe facial and upper body injuries in the event of a serious impact. Optimum protection can only be ensured when used in conjunction with a conventional three point safety belt. The safety belts form an integral part of the Supplementary Restraint System (SRS).

The visible VIN plate shows the air bag symbol and either X1 or X2 depending on the number of air bags fitted, is attached to the windshield edge of the instrument panel.







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.

It is not possible under any circumstances to disable the passenger air bag while maintaining the integrity of the whole system.

The system consists of:
^ Air bag control module
^ Wiring harness
^ Air bag sliding contact
^ Air bag indicator
^ Safing sensor
^ Air bag module(s)

The electronic air bag control module is mounted horizontally to the floor pan beneath the floor console, to facilitate impact sensing along the longitudinal axis. The air bag control module retains full control of the air bag system at all times, providing continual systems checks and maintaining a full diagnostic function. The air bag control module stores any faults detected during a driving cycle in a non volatile memory, which can be accessed through the diagnostic connector (DLC) using appropriate test equipment. The air bag control module indicates the presence of a fault by flashing the air bag warning indicator after the initial prove out sequence. The behavior of the warning indicator depends on the type of fault present.

Air Bag Indicator:

If the air bag warning indicator fails, the air bag control module uses the secondary air bag warning indicator. The secondary air bag warning indicator will only flash if there is a fault present and the primary air bag warning indicator is inoperative.

The air bag control module provides a back up power supply, sufficient to deploy the air bag(s) for a maximum of 150mS after power loss. The back up power supply is discharged by the electronic air bag control module within 60 seconds of the battery ground cable being disconnected.

The air bag control module contains a micro controller to evaluate and process impact data an electronic accelerometer, which measures the actual acceleration and deceleration along the vehicle's longitudinal axis and an electro- mechanical safing sensor. When both these sensors detect an impact in excess of a predetermined limit, the deployment sequence will be initiated by the air bag control module to deploy the frontal air bag(s). The two sensors working together prevent unintentional deployment of the frontal air bag(s).

The air bag warning indicator is located in the instrument cluster. It illuminates for approximately six seconds when the ignition is turned ON and then will go OFF unless a fault is detected. If a fault is detected the warning indicator will start to flash after another 5 seconds.

The sections of wiring harness which carry air bag wiring are marked by yellow insulation to aid identification of the air bag wiring harness routing.

The air bag sliding contact is designed to carry signals between the air bag control module and the driver air bag module. The sliding contact is attached to the steering Column switch mounting bracket 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 sliding contact is used in order to achieve the high degree of circuit integrity required by the Supplementary Restraint System (SRS).

The driver and passenger air bag modules consist of the following components which cannot be disassembled:
^ Inflator
^ Bag
^ Container
^ Cover

The inflator is screwed into a metal cup-shaped container. The bag is then folded on top of the inflator and the whole subassembly is closed by the cover.

The driver air bag module is attached to the steering wheel, the cover forming the outer surface of the steering wheel boss. The cover has invisible 'split lines' moulded in its surface allowing the air bag to easily exit though the cover when the system deploys.

The passenger air bag module is located above the glove compartment and is integrated into the instrument panel to provide an unobtrusive appearance. The cover is a one piece moulding which is attached to the instrument panel along the windshield edge, and by two plastic shear bolts along its front edge. As the air bag deploys, the cover is forced free of the plastic shear bolts, but remains attached to the instrument panel.

Driver And Passenger Air Bag Module Inflator:

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 an electrical current 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 driver air bag module has one inflator and bag, with a filled volume of 30 litres. The passenger air bag module has one inflator and bag, with a filled volume of 60 litres.

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 suit the vehicle proportions.

The air bag system retains a direct independent battery feed which allows the system to retain sufficient voltage to deploy the air bag modules should battery or ignition power be lost during an impact, maintaining a constant state of readiness.







The Safety Restraint System fitted to these vehicles will communicate faults/concerns detected by the air bag control module during a driving cycle or after initial key on by means of a warning indicator contained within the instrument cluster.







If a concern is detected, the control module will communicate by flashing the warning indicator to give a Diagnostic Trouble Code (DTC).