Subaru Legacy/Outback

1999-2003 of release

Repair and operation of the car

System of additional safety (SRS) - the device and the principle of functioning

At a head-on collision which sufficiency of intensity the processor (CPU) forward sensors on pravlenny overloads, and also the control and electric sensors which are built in the module of management provide short circuit of a chain of activation of frontal safety cushions of the driver and forward passenger.

Necessary condition for operation of modules of safety cushions is simultaneous short circuit of chains of both managements of SRS sensors which are built in the module.

Control sensors of lateral safety cushions are built in the corresponding sensors of the directed overloads and work at registration of the directed lateral overloads exceeding a certain value, - simultaneity of operation of the sensor of an overload and the control sensor, besides, is an indispensable condition of activation of a pillow.


Module of management of SRS

The module of management of SRS is located in forward part of the tunnel canal of the forward panel of a floor and provides giving of power supply to modules of safety cushions at the time of the collision causing rather strong directed overloads. Operation of system happens even in case of crash of the onboard battery.

A survey of a condition of the SRS components is carried out by the module at each start of the engine and is followed by short-term operation of the control lamp of "AIR BAG/SRS" which is built in in an instrument guard. In case of an exit any of knots out of operation the control lamp after implementation of start is not disconnected. Also operation of a control lamp during the movement testifies to malfunction in system, - in a similar situation the car should be driven away as soon as possible on car repair shop.

SRS sensors

Forward sensors of the directed overloads

Sensors are installed ahead of both forward wheel arches. Sensors have a pendular design which anchor knot at excess by the directed blow of some limit admissible value turns and provides short circuit of the corresponding electric chain.

Lateral sensors of the directed overloads

The principle of operation of lateral sensors of the directed overloads is similar described above for forward sensors.

Control and electric sensors

Control and electric sensors are built in the module of management of SRS, and also assemblies of both lateral sensors of the directed overloads.

The control sensor, as well as sensors of the directed overloads, has a pendular design and acts as a safety element at short circuit of the corresponding chain of SRS.

The electric sensor consists from sensitive to the directed overloads of a semiconductor element which resistance changes depending on intensity of blow. The sensor allows CPU to estimate intensity of the overloads arising at collision.

Modules of safety cushions

Design of modules of frontal safety cushions

1 — the Safety cushion 2 — the Gas generator 3 — the Cover 4 — the Gas generator 5 — the Bearing beam of a steering column

Activation of a pillow (ek) of safety happens on condition of simultaneous operation of the corresponding SRS sensors (see above). Short circuit of a chain of the module of a safety cushion leads to almost instant filling of the last with the nitrogen which is allocated as a result of combustion of powdery mix of azid of sodium with copper oxide. In case of failure of the onboard battery the system switches to food from the reserve source which is built in in the SRS module and providing autonomous power generation within about 20 more seconds. The design of modules of safety cushions is presented on illustrations.

Contact drum

The reel is installed between a steering column and a steering wheel and presents itself the sliding contact made the spiral of a flat cable vein twisted in the form. By means of a contact drum giving of food from a plait of an electrical wiring of a steering column to placed in a nave of a steering wheel (and therefore mobile) is provided to the module of a driver's safety cushion.

Connecting electrical wiring

Connecting wires of SRS can be easily distinguished from an other onboard electrical wiring on bright yellow color of isolation.

Contact SRS sockets are painted in yellow, or blue colors (see the Section Diagnostics of Malfunctions of SRS).

Emergency natyazhitel of seat belts

otsedura of removal/installation of emergency natyazhitel, and also order of their utilization are described in the Section Seat belts - the general information, check of a state, removal and installation, an order of utilization of not worked emergency natyazhitel.

Seat belts of both forward seats are equipped by automatic emergency natyazhitel which activation happens at the command of the module of management of SRS developed on the basis of the analysis of the data arriving from forward sensors of the directed overloads (on condition of short circuit of the built-in control sensors). The basis of a design of natyazhitel is made by the assemblies of the belts of returnable drums which are taking up tapes equipped with the built-in gas generators.

Design of an emergency natyazhitel of a seat belt

1 — the Seat belt 2 — the Returnable device 3 — the Leading-up levels	4 — the Shaft 5 — Gas 6 — the Torsion bar

At receipt of the corresponding team from the module of management of SRS gas generators of natyazhitel are activated and the weak point of seat belts instantly gets out returnable devices. At excess by load of a belt of some limit admissible value the torsion bar which is built in assembly of a natyazhitel is twisted, weakening thereby the impact made by a belt tape on a thorax of the fastened driver/passenger.

Upon completion of operation of an emergency natyazhitel the returnable drum remains is blocked and assembly of a seat belt is subject to replacement.

Precautionary measures

Check of a condition of SRS has to be made time of 10 years.

Dismantle and service of components of a steering column, the radio receiver and other components located near the dashboard demands observance of special precautionary measures as casual damage of an electrical wiring of SRS can lead to the unauthorized operation of safety cushions fraught with receiving severe injuries. It is easy to identify an electrical wiring of SRS on bright yellow coloring of isolation, - at all do not disunite its contact sockets and do not connect to them any electric diagnostic units.

Before starting performance of any works near the SRS components in surely order disconnect system!

The module of a safety cushion removed from the car should be held the face from itself, - transfer assembly to a safe place and lay face up.

Do not try to perform measurement of resistance of the SRS components at all, - the energy developed by the internal power supply of an ohmmeter can quite enough for operation of gas generators!

Before using on the car any electronic equipment it is necessary to make surely shutdown of SRS (see below).

Do not throw out never the worked modules of safety cushions in garbage recipients at all, - advice on utilization of the SRS components can always be got at car repair shops.

Shutdown of SRS system

Make the following manipulations for shutdown of SRS:

a) Bring the operated car wheels into rectilinear situation, turn the ignition key in the situation LOCK and take it from the lock;
b) Switch off ignition;
c) Disconnect from the battery at first negative, then positive wires.

If the stereosystem established on the car is equipped with a security code before disconnecting the battery make sure that have the correct combination for input of the audio system in action!

d) Before starting performance of any works, wait not less than 20 seconds during which there has to be a discharge of the condenser of the emergency SRS power supply.

Activation of SRS

For activation of system connect to the battery at first a positive wire, then - negative, turn the ignition key in situation and make sure of serviceability of operation of a control lamp of SRS.