Subaru Forester

1997-2005 of release

Repair and operation of the car

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

General information

Some of the models considered in the present manual are equipped with system of additional safety (SRS) better known under the name of safety cushions. The system provides additional protection of the driver and forward passenger of the car at strong front and (at the corresponding complete set) side blows. The module of a driver's frontal safety cushion is placed in a stupichny part of assembly of a steering wheel (see the Head Podvesk and steering).

The module of a passenger safety cushion is located on the right under the car dashboard on which surface at the same time the warning inscription in the form of an abbreviation of SRS or AIR BAG is applied. Side safety cushions (at the corresponding complete set of the car) are built in in external sidewalls of backs of front seats.

The control lamp of SRS/AIR BAG, spring contact drum of assembly of understeering switches, the module of management (ECU) of SRS with built in in it by the sensor of the directed overloads (G-sensor) and the control sensor, individual sensors of the directed overloads of safety cushions and a connecting electrical wiring are among the other SRS components.

Scheme arrangement of the SRS components

1  —  Assembly of the combined understeering switches with a spring contact drum
2  —  Fixing bolts with heads like TORX (T30)
3  —  the Module of a driver's safety cushion
4  —  the Module of a passenger safety cushion
5  —  the Module of management of SRS
6  —  Fixing bolts with heads like TORX (T40)
7  —  the Sensor of a side safety cushion
8  —  the Module of a side safety cushion

9  —  the Electrical wiring of a chain of the left side safety cushion
10  —  the Electrical wiring of a chain of the right side safety cushion
11  —  the Main plait of an electrical wiring of SRS
12  —  the Sensor of the right forward safety cushion
13  —  the Electrical wiring of a chain of the right forward safety cushion
14  —  the Electrical wiring of a chain of the left forward safety cushion
15  —  the Sensor of the left forward safety cushion

Principle of functioning of SRS

At strong front blow of the car the sensors of forward safety cushions and also which are built in the ECU SRS G-sensor and the control sensor provide short circuit of a chain of activation of pillows.

Necessary condition for operation of modules of safety cushions is simultaneous short circuit of chains both built in in ECU SRS sensors.

Control sensors of side safety cushions are built in the corresponding sensors of the directed overloads and work at emergence of the directed side 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).

Modules of safety cushions

Activation of a pillow(s) of safety happens on condition of operation of sensors of the directed SRS overloads. 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 emitted as a result of combustion of powdery mix of azid of sodium with copper oxide.

In case of failure of the onboard rechargeable battery the system switches to food from the reserve source which is built in in the SRS module and providing autonomous power generation within 20 more seconds. It is necessary to notice that the passenger safety cushion usually is more on volume, than driver's, and it is equipped with the metal bearing case, at operation of the module which is divided into two half and a finishing cover.

Spring contact drum

The reel is installed on steering columns and presents itself contact in the form of a spiral spring. By means of a contact drum giving 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.

Module of management

ECU SRS 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 rechargeable 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 the dashboard of the car. In case of an exit of any of knots out of operation shutdown of a control lamp does not occur. Also operation of a control lamp testifies to malfunction in system during the movement, - in a similar situation the car should be driven away as soon as possible on car repair shop.

Precautionary measures

Check of a condition of SRS has to be made time in 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 the 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 any electronic equipment on the car it is necessary to make surely shutdown of SRS (see below).

Never throw out 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 the SRS system

Make the following manipulations for shutdown of safety cushions:

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

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

SRS activation

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.