Ford Workshop Service and Repair Manuals

The supplementary restraint system (SRS) is fitted as standard for the driver and optionally for the front seat passenger. The supplementary restraint system has been specifically designed to protect the driver and passenger (when optional passenger air bag is fitted), 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 seat belt. The seat belts form an integral part of the supplementry restraint system.

The visible VIN plate shows the air bag symbol and either X1 or X2 dependant on the number of air bags fitted.

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

The system consists of:

The electronic air bag control module governs the operation of the whole system, including the diagnostics element. It contains two sensors, a crash sensor and a safing sensor. The crash sensor produces a signal corresponding to the rate of deceleration. The safing sensor detects only deceleration. These two sensors are connected in series and if they both sense a deceleration in excess of a predetermined limit, the electronic air bag control module will deploy the pyrotechnic pretensioners and the air bag module(s). The system will always deploy the pyrotechnic pretensioners before or at the same time as the air bag(s) and in that sequence only.

Vehicles with mechanical seat belt retractor pretensioners operate in the same sequence, the exception being that the pretensioners are deployed mechanically, by the inertia of an impact.

The electronic air bag control module also performs system checks. In the event of a fault being found the warning light is illuminated either constantly or intermittently. The behaviour of the warning light depends on the type of fault present. The warning light is located within the instrument cluster.

The wiring harness provides power to the electronic air bag control module from the vehicle supply and hence to the air bag module(s) and warning light.

The air bag clockspring is designed to carry signals between the electronic air bag control module and the driver air bag module. The air bag clockspring is fitted 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 electronic air bag control module and the air bag module. The clockspring is used in order to achieve the high degree of circuit integrity required by such a critical safety system as the supplementary restraining system (SRS).

The driver and passenger air bag modules consist of the following components which cannot be disassembled:

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

The passenger air bag module is located above the glove compartment and is integrated into the crash pad/facia to provide an unobtrusive appearance. The cover has invisible `split lines' moulded in its surfaces allowing the air bag to easily exit through the cover when the system deploys.

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 electronic 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 one air bag, with a filled volume of 30 litres. The passenger air bag module has two inflators and a single air bag having 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 the vehicle proportions.