AIR BAG SYSTEM

Description 5580C

GENERAL VIEW

The following figure shows the complete configuration of the Air Bag system.

1 - Electronic control unit

2 - Passenger''s Air Bag module

3 - Key switch for disabling the passenger''s front Air Bag

4 - Passenger''s pretensioner

5 - Passenger''s Side Bag module

6 - Passenger side impact satellite sensor

7 - Passenger''s Window Bag module

8 - Driver''s Window Bag module

9 - Driver''s Side Bag module

10 - Driver''s side impact satellite sensor

11 - Driver''s pretensioner

12 - Air Bag system failure warning light

13 - Passenger Air Bag deactivation warning light

14 - Driver''s Air Bag module

15 - Clock spring

INTRODUCTION

The Air Bag system used on the car intervenes, in the case of front or side impacts of medium-high severity, to protect the occupants of the front seats and the heads of the occupants of the side rear seats. The system is completed by the presence of pretensioners on the front seat belts which, to optimise their retaining action, have a load limiter. The load limiter is also presnt on the rear seat belt winders

Characteristic of working principle 7065 SEAT BELTS AND ACCESSORIES

So that the Air Bag system can carry out its function with the maximum efficiency, the seat occupants MUST wear their seat belts correctly.

The components of the Air Bag system have been designed to work on a specific car. They therefore may NOT be tampered with, adapted or installed on other types of vehicles. Any attempt to reuse, adapt or install them on a different type of vehicle could cause severe or fatal injury to the occupants, both in the case of normal use and in the event of a crash.

A control system managed by the electronic control unit, in the case of a front or side impact, controls the partial or total activation of the devices.

The Air Bag system components are connected electrically by dedicated wiring, integrated in the dashboard wiring loom for the front devices, and in the rear wiring loom for the side devices.

The control unit is connected to the system by means of two connectors, one for the front cable and one for the rear cable.

The passenger''s front Air Bag module can be deactivated voluntarily, by a specific key switch located beside the dashboard. The deactivation of the passenger''s front Air Bag module does not disable the side Air Bag modules. Thus in the evente of a side impact, protection is also offered to any child who may be on board.

If a child seat is fitted on the front passenger seat, the front Air Bag module MUST be deactivated.

If the module is deactivated, a passenger seated on the front seat is protected only by the seat belt with pretensioner and the side Air Bags.

the activation of the Air Bags releases a small amount of powder. This powder, which may be deposited on the opened cushions and inside the vehicle, is not harmful but could irritate the skin and eyes. In case of exposure, wash with neutral soap and water.

The Air Bag system components last different lengths of time.

They should therefore be replaced in accordance with the following deadlines:

• Airbag modules: 14 years
• Clock spring: 10 years
• Pretensioners: 10 years

To indicate the state of efficiency, the system has:

• fault warning light (red) on the instrument panel;
• passenger''s Air Bag disabled warning light (yellow) on the instrument panel;
• serial diagnostic serial, integrated in the EOBD socket, for checking efficiency using the EXAMINER.

COMPOSITION

The Air Bag protection system comprises the following:

• an electronic control unit;
• two side impact sensors (right and left);
• a switch for disabling the passenger''s Air Bag;
• two front Air Bag modules for protecting the front seat occupants;
• two side protection Air Bag modules (chest, abdomen) for the front seat occupants;
• two side Air Bag modules protecting the heads of the front seat occupants and the rear side seats.
• two seat belts with pretensioners on the front seats.

ELECTRONIC CONTROL UNIT

View of control unit''s position of assembly.

1 - Electronic control unit

2 - Arrow indicating direction of travel

3 - Attachments

4 - Electrical connections

5 - Control unit''s earth contact

Specifications

The electronic control unit manages the entire system, checking all the components, and has the function of recognising a crash situation promptly and activating only the pretensioners or the pretensioenrs and the Air Bag modules, depending on the type and severity of the crash.

The control unit is fixed rigidly to the bodywork, under the central console near the centre of gravity, to allow the deceleration sensors it contains to detect precisely the deceleration of the car.

The control unit must always be fitted with the arrow stamped on the adhesive plate facing the vehicle''s direction of travel. Always check that there are no foreign bodies between the control unit and the bodywork, and tighten the bolts to the specified torque.

Components

The following figure shows the control unit.

1 - Control unit

A - 24-pin connector for facia cable

B - 32-pin connector for rear cable

Control unit pin-out

Dashboard cable CONNECTOR A (24-way)

Rear cable CONNECTOR B (32-way)

The control unit contains two deceleration sensors, one electronic and the other an electromechanical safety sensor which has the function of giving enablement to activation, working independently from the electronic sensor.

If the car''s deceleration value, measured by the electronic sensor and processed by the processor in terms of severity of the crash, exceeds the severity level established for the command to activate the devices, the control unit makes sure that this command can only be sent if, at the same time, the safety sensor is closed.

To ensure the correct management of the system, the following functions are present:

• accumulation of energy: the control unit is supplied at 12V with key in the ON position, but can operate for a few fractions of a second if the supply voltage is interrupted or drops, so as to ensure operation of the system and write the data in the crash memory.
• check of earth attachment: the control unit''s control logic checks the electrical contact between the bodywork and the control unit;
• fault memory: with the ignition on, the control unit continuously checks that the circuit is working (including the energy reserve circuit), during normal operation of the car and during normal operation of the car and during any crashes, and tests all the electrical parts of the system, indicating the presence of faults by switching on the Air Bag fault warning light on the instrument panel and memorising the fault code.
• crash memory: this records the information, relating to crash events, which have led to the activation of the pretensioners and modules, front or side.

In view of the importance of its functions, the control unit is designed in such a way that it cannot be opened with leaving visible signs of having been tampered with.

If the control unit is dropped or is subjected to unusual impact during handling, the control unit MUST be replaced.

Operation

In the case of a frontal impact, the electronic sensor detects a deceleration signal along the vehicle''s longitudinal axis. If the signal, processed by the control unit''s processor, indicates a crash severity such as to require the intervention of the system and if, at the same time, the safety sensor is closed (enablement for activation), the control unit, as the first intervention level, commands the activation of only the pretensioners or, in the case of a more severe impact, the pretensioners and front Air Bags (activation of driver''s module only if the passenger''s module has been deactivated).

As with a side impact, the satellite sensors, located in the central pillars, detect the direct crash signal along the car''s transversal axis, and send it to the control unit. If the severity of the crash is such as to require the system''s intervention, if the information from the satellite sensors corresponds to that from the safety sensor, the control unit commands the activation of the modules on the side affected by the crash. The side modules are activated independently of each other (driver''s or passenger''s) and of the front modules.

The activation of the front Air Bags is always preceded by the activation of the pretensioners, unless the pretensioners have been activated in a previous crash and have not yet been replaced.

The system activation times are in the order of thousandths of a second and anticipate the movements of the occupant''s body following the impact.

After each activation of one of the systems operated (pretensioners, front Air Bags, side Air Bags), the control unit memorises the activation in non-deletable memory and causes the fault warning light on the instrument panel to come on.

Before being replaced, the control unit guarantees the activation of the individual devices within the following limits:

• 3 impacts with activation of the front seat belt pretensioners only;
• 3 impacts in total with activation of the side Air Bags (right or left)
• 1 impact with activation of the pretensioners and front Air Bags;
• any combination of the above cases until one of the limits indicated is reached.

If one of the limits described has not been reached, it will be possible, after restoring the operating conditions of the system, to reuse the control unit after carrying out the RESET procedure by means of the EXAMINER. The last activation, for each of the sequences, will prevent further reset conditions.

The Air Bag system does not intervene in the case of a rear collision or if the vehicle overturns.

System autodiagnosis

The control unit carries out a continuous self-test of the system''s operation. In particular:

• it detects and memorizes any faults
• it recognizes the various components and the type of fault;
• it signals the onset of these faults via the special warning light in the instrument panel.

The faults memorised in the control unit may only be deleted after the fault has been repaired using the EXAMINER diagnostic equipment.

If a fault is detected in the passenger Air Bag disabling switch, for safety reasons this is considered by the control unit to be in the OFF position, so the operation of the module is inhibited and the warning light on the instrument panel comes on.

AIR BAG SYSTEM FAILURE WARNING LIGHT

View of position on instrument panel

Specifications

During starting, key in key-on position, the fault warning light (red) comes on for about four seconds (initial self-test stage) and then goes out. If the control unit detects a fault in the warning light, it memorises the corresponding fault code. If no faults are detected in the system at key-on, and there are no fault conditions in the fault memory, the warning light goes out after four seconds of self-test, otherwise it stays on until key off.

Operation

The warning light remains on or comes on, during the normal operation of the vehicle, in the following cases:

• the control unit detects a fault in the Air Bag system;
• the control unit detects an impact with activation of the system;
• the control unit detects a fault in the actual warning light connection circuit.

As a result of an impact with the intervention of only the pretensioners or side Air Bags, the warning light stays on until the system''s operating conditions are restored (replacement of the component concerned and rest of the control unit using the EXAMINER).

if the impact causes the intervention of the front Air Bag modules, the warning light stays on permanently, and the control unit cannot be reset (in this case the control unit must be replaced).

If internal operating faults arise during the control unit''s operating life, and these faults cannot be reset by the EXAMINER, they are indicated by the warning light staying on permanently.

PASSENGER''S FRONT AIR BAG DISABLED WARNING LIGHT

View of position on instrument panel

Specifications

With the key at the key-on position, the passenger''s Air Bag disabled warning light (yellow) comes on for about four seconds (initial self-test stage). If the control unit detects a fault in the warning light, it memorises the relevant fault code, switches on the fault warning light and keeps the passenger''s Air Bag module disabled. Restore the system''s operation using the EXAMINER, in the same way as for the fault warning light.

After the initial four-second self-test stage, if the disabling key switch is turned to the OFF position, the warning light stays on indicating that the passenger''s module is disabled. If there are no faults, the light flashes for a further four seconds and then goes out, indicating that the passenger''s module is enabled.

The passenger''s module MUST be disabled only using the ignition key (ignition switch at STOP position) - (DO NOT USE a second ignition key for disablement).

DRIVER''S AIR BAG MODULE

The following figure shows a view of the assembly

1 - Casing

2 - Cover

3 - Bag

4 - Gas generator

5 - Warning plate

6 - Point of connection to electrical system

Specifications

The Air Bag is a passive safety device made up of a bag which, in the case of a frontal impact, automatically inflates placing itself between the body of the driver and the structure of the front part of the passenger compartment. The Air Bag module is installed in the centre of the steering wheel, and its cover also acts as the horn control.

Components

The module comprises:

• a plastic cover; which in the case of activation tears in predefined points to allow the bag to expand correctly;
• a bag, with a volume of about 42 litres, made of nylon fabric to minimise skin abrasions in the case of contact, and folded in a particular way so that it inflates gradually and not directly facing the driver;
• a pyrotechnic gas generator
• a casing.

On the bottom of the gas generator, there is a warning plate which gives the instructions for handling (

Characteristic of working principle 5580C AIR BAG SYSTEM

).

Operation

The gas generator for inflating the module is electrically activated by a signal coming from the electronic control module. Following this signal, a pyrotechnic charge contained in the generator is triggered. The gases produced by the combustion of the charge flow through special holes and expand in the bag, causing the cover to tear at the specific points. When fully inflated, the cushion is in the optimum position to carry out its function to retain the occupant. After being inflated by the gas, the bag deflates immediately through specific vent holes.

CLOCK SPRING

The following figure shows a view of the assembly

A - Clock spring for versions with radio/Selespeed controls on the steering wheel

B - Clock spring for versions with radio/Selespeed controls on the steering wheel

1 - Clock spring

2 - Electrical connection for connecting Air Bag module

3 - Electrical connection for connecting horn

4 - Rotation lock ring

5 - Safety key

6 - Point of connection to electrical system

Specifications

The Clock Spring is a device which allows the connecting cables for the Air Bag module and other electrical controls installed in the steering wheel to follow the steering wheel rotation without the risk of breaking.

The device, consisting of two plates is secured by means of the lower plate to the stalk unit, and is joined to the steering wheel by means of specific recesses on the upper plate. The connection to the electrical system is via the connection points, present on the edge of the lower plate.

Components

The clock spring has two cables on the steering wheel side, one of which is for connecting the Air Bag module, and one connects the steering wheel''s electrical functions. The latter connector may be two- or eight-pin, depending on the versions.

On the upper plate, steering wheel side, there is a ring which automatically blocks the rotation between the two plates when the device is removed from the steering wheel.

The new device is supplied with a safety key for transport, to be removed before fitting.

Operation

Inside the two plates, the connecting cables for the Air Bag module and the various electrical functions are wound in a spiral, with a sufficient number of coils to follow the steering wheel''s rotations. The upper plate rotates by means of the recesses present inside the locking ring which fit in the seating on the steering wheel hub. In the working position, the steering wheel presses on the ring, freeing it from the recesses, thus unlocking the rotation between the two plates. When the steering wheel is removed, pushed by a spring, it blocks the rotation between the two plates. This function prevents the top plate, no longer locked to the steering wheel, from turning freely and causing the sprial inside the device to unwind or wind and then possibly break.

In operations involving the removal of the steering wheel and the device, the following must be observed:

• always operate with the wheels lined up straight;
• for safety, lock the clock spring with a band before removing it from the stalk unit.

PASSENGER AIR BAG MODULE

The following figure shows a view of the assembly

1 - Metal mounting

2 - Bag cover

3 - Warning plate

4 - Connecting point

5 - Gas generator

6 - Folded bag

Specifications

The passenger''s Air Bag module is located inside the dashboard, near a foam rubber flap in the trim, above the glove compartment, and is secured by brackets to the crossmember. As for the driver''s module, it intervenes to provide front protection for the passenger, in the event of crashes which exceed a particular threshold, and can also be specifically disabled.

Components

The module comprises:

a metal mounting containing the gas generator and bag;

a card cover which, in the case of activation, tears to allow correct expansion of the bag;

a bag, with a volume of about 90 litres, made of nylon fabric in order to minimise skin abrasions in the event of contact, and folded in a particular way;

a gas generator consisting of a pressurised gas container holding a pyrotechnic charge;

a point for connection to the electrical system;

On the bag cover there is a warning plate which gives the handling instructions (see

Characteristic of working principle 5580C AIR BAG SYSTEM

).

Operation

The gas generator for inflating the module is electrically activated by a signal coming from the electronic control module. Following this siganl, a pyrotechnic charge is triggeed which causes the gases contained in the generator to expand. The gases expand, coming out of specific holes, and inflate the bag. The increase in volume of the bag causes the retaining clips to break and the flap built into the dashboard to open, thus allowing the bag to come out correctly.

To prevent the flap being projected onto the passenger when the bag inflates, the flap is secured to the crossmember by a retaining belt. When fully inflated, the cushion is in the optimum position to carry out its function to retain the occupant. After being inflated by the gas, the bag deflates immediately thanks to the permeability of the fabric.

The flap can only be removed from the dashboard by breaking the prings which must, in that case, be replaced.

PASSENGER AIR BAG DISABLEMENT KEY SWITCH

View of location on car

1 - Key switch

2 - OFF position: passenger''s Air Bag disabled

3 - ON position: passenger''s Air Bag enabled

4 - Passenger''s Air Bag disabled warning light

Specifications

A switch operated by the ignition key allows the passenger''s Air Bag module to be enabled (ON) or disabled (OFF). The switch is located at the end of the dashboard on the passenger side, and is only accessible with the door open.

Components

The diagram below shows a view of the assembly.

1 - Casing

2 - Switch

3 - Key barrel

4 - Plate

The unit consists of a casing containing the switch, a key barrel inserted in the casing and held by a clip and a plate which indicates the position assumed by the switch (ON or OFF). On the casing, there is also the seating for the connector to the electrical system.

Any faults in the switch are indicated by the Air Bag system fault warning light coming on.

Operation

The switch can be operated by the car''s ignition switch whenever the activation of the passenger''s front module is to be enabled or disabled.

The electronic control unit checks the status of the switch during the normal diagnostic procedure at Key On (four seconds). If the recognised state is OFF, it excludes the module from possible activation, memorises the corresponding signal and causes the passenger Air Bag disabled warning light on the instrument panel to come on. If the recognised state is ON, after the four seconds of the diagnostic procedure the warning light flashes for a further four seconds and then goes out.

The remaining side Air Bags are not affected by deactivation commands.

In the case of faults in the switch, the system ensures the following:

• it does not activate the passenger module
• it causes the Air Bag fault warning light to come on
• it causes the passenger Air Bag disabled warning light to come on
• it memorises the state of deactivation.

Do not operate the switch with the ignition key in the ON position (e.g. by using the second key). In this case the electronic control unit would memorise a fault, indicating it by switching on the Air Bag fault warning light and deactivating the module.

SIDE BAG MODULE

The figure below shows a view of assembly.

1 - Side Air Bag module

2 - Seat cover

3 - Seat structure

4 - Supply cable

5 - Connector

Specifications

To provide maximum protection to the front seat occupants in the event of side impacts, there are side Air Bag modules installed on the seat squabs, on the side facing the outside of the car, under the cover.

This conformation is considered to be the most efficient as it always enables the Air Bag to be in the optimum position in relation to the occupant, irrespective of the seat adjustment or size of the occupant.

The side Air Bag mainly protects the chest and abdominal region, even if the occupant is not seated correctly, as the dynamics of opening of the bag minimises the risk of damage to the body caused by the impact with the Air Bag.

Do not put covers on the front seat squabs.

Do not wash the seat squab with water or pressurised steam.

Components

View of Side Bag components

1 - Outer cover

2 - Container

3 - Point of electrical connection

4 - Gas generator

5 - Folded bag

6 - Warning plate

The side Air Bag module consists of a plastic container holding the gas generator and a permeable nylon bag with a volume of about 12 litres.

The module''s container has a cover with predetermined break zones which, with the seat squab cover fitted, line up with easy-open sections of seam on the outside of the seat cover.

On the bottom of the container, there is a warning plate which gives the instructions for handling the module (

Characteristic of working principle 5580C AIR BAG SYSTEM

).

The connection of the module to the electrical system is by means of two cables with yellow sheath, contained together with the seat''s earth lead in a fabric-coated duct secured to the seat frame. The two cables end with a yellow connector. The connectors for the module, seat belt fastened sensor (driver''s side only) and seat pad (if present) are fixed on a removable mounting located on the bottom of the seat.

To remove the connector mounting, press on the anchoring clip which is positioned at the point indicated in the figure below.

View of connector mounting on seat.

1 - Removable mounting

2 - Side Bag connector

3 - Heating pad connector

4 - Seat belt fastened connector

5 - Anchoring clip

Operation

The gas generator for inflating the module is electrically activated by a signal coming from the electronic control module. Following this siganl, a pyrotechnic charge is triggeed which causes the gases contained in the generator to expand. The gases expand, coming out of specific holes, and inflate the bag. The increase in volume of the bag causes the container to break in the predetermined areas and the seams on the seat squab cover to open along the preset sections, thus enabling the bag to come out correctly. After completion, the bag is in the optimum position for carrying out its function of protecting the occupant. After being inflated by the gas, the bag deflates immediately thanks to the permeability of the fabric.

No operations, other than removing and refitting the seat from the vehicle, can be carried out on a seats equipped with a Side Bag. It is absolutely prohibited to disassemble seats fitted with a Side Bag; these operations should be carried out by suitably trained and authorized personnel.

CURTAIN SIDE AIR BAG MODULE (WINDOW BAG)

General view

1 - Connector

2 - Gas generator

3 - Bag retaining bands

4 - Bag

5 - Strap

6 - Ceiling trim

Specifications

On all versions of the car, there is a system for protecting the heads of the front and rear side occupants.

Apart from the vehicle''s structural characteristics, the Side Bags are the only passive protection system in the case of a side impact. The head protection Air Bags (Window Bags), in addition to the Side Bags and front Air Bags, offer the rear seat occupants the maximum possible protection in the event of a crash, also eliminating the risk of injuries to the arm and shoulder and protecting the heads of the rear side seat occupants.

Among the different types of Window Bag, the curtain system is the one which offers the best performance thanks to the large area of expansion and its self-supporting capacity, also in the absence of support if the side windows break during the impact.

Components

View of the Window Bag components

1 - Anchoring strap

2 - Bag containing sleeve

3 - Bag

4 - Flexible tube

5 - Retaining clamps

6 - Bag retaning bands

7 - Mountings

8 - Gas generator

9 - Warning plate

10 - Connector

The Window Bag module consists of:

• a gas generator secured by appropriate mounting to the car''s rear pillar;
• a permeable fabric flexible tube, secured by a band to the gas generator, which diffuses the gas evenly along the whole length of the bag;
• a bag, secured to the gas generator together with the flexible pipe, is made of a nylon permeable fabric and is folded inside a containing sleeve. The bag is designed so that, when inflated, it correctly absorbs the energy of the impact, holding the heads of the occupants an appropriate distance from the impact zone. After inflation, the gas deflates immediately through the porous fabric.
• plastic easy-open clamps for securing the bag to the ceiling longitudinal member;
• a retaining strap which holds the inflated bag in position;
• a connector for connection to the electrical system;
• a warning plate which gives the instructions.

Operation

The gas generator for inflating the module is electrically activated by a signal coming from the electronic control module. Following this siganl, a pyrotechnic charge is triggeed which causes the gases contained in the generator to expand. The gases expand and emerge through specific holes and are distributed evenly along the length of the bag via the flexible pipe, inflating the bag. The increase in volume of the bag causes the fixing clamps to break, the sleeve seams to yield and the finishing trim to open, designed so as to allow the bag to emerge correctly downwards. The correct unfolding of the bag is ensured by a retaining strap, present at the front end of the bag. After completion, the bag is in the optimum position for carrying out its function of protecting the occupant. After inflation, the bag deflates immediately because of the permeability of the fabric.

SIDE IMPACT SATELLITE SENSORS

View of sensor

1 - Side impact satellite sensor

2 - Connecting connector

3 - Centring pin

Specifications

Apart from the Air Bags, the side protection system also comprises the electronic control module which ensures correct operation. To measure the acceleration resulting from a side impact, there are two satellite sensors installed in the side pillars, containing an accelerometer.

Components

The side impact satellite sensor consists of a casing containing the acceleration sensor. At the rear of the casing, there is a pin for correct positioning in the seating. On the casing, there is also a connection point for connection to the electrical system.

Operation

If the acceleration value measured by the sensor in question causes a particular threshold to be exceeded, this information is compared with the measurement obtained from the safing sensor contained in the Air Bag system''s electronic control unit. If the values measured are consistent, the control unit causes the activation of the Air Bags on the side affected by the impact.