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Brief description, anti-theft alarm

Brief description, anti-theft alarm


The theft protection of the car consists of two functions, immobilizer which is standard on all cars except cars with OBDII which has a simpler form of so called start interlock and theft alarm as an option. The theft protection functions are controlled by TWICE.

Immobilization

The immobilizer prevents the car starting if the wrong key is used. The fuel supply is shut off and the starter motor relay blocked. The car key contains a transponder with a unique identification code which is received by a receiver unit. The receiver is located in the ignition lock.

The receiver, which is connected to TWICE, sends the code to TWICE which is programmed to recognise the car keys. If the right key is inserted in the ignition switch (ignition position ON), the engine can be started. If a faulty transponder or one which does not belong to the car is used, “KEY NOT ACCEPTED” appears on the SID display.

In the event of a fault on the receiver unit or transponder, the remote control can be used instead to mobilise the car. The car can be mobilised by pressing a button on the remote control after the ignition key has been turned to the ON position.

Anti-theft alarm

The anti-theft alarm can be factory-fitted or installed as an accessory.

The anti-theft alarm is armed/disarmed using the remote control. On US/CA/LA markets, it can also be armed/disarmed using the key in the driver's door or tailgate (disarm). If the anti-theft alarm is armed and the key is put in the ignition and turned, the alarm is disarmed when the correct identification code is received from the transponder.

The anti-theft alarm has the following inputs for tripping the alarm:


• Door switches

• Switch, luggage compartment illumination

• Bonnet switch, anti-theft alarm

• Ignition lock (position ON with incorrect key)

• Glass breakage sensor

• Angle sensor (accessory)


A tripped alarm is indicated by:


• Direction indicators

• Siren, anti-theft alarm


The behaviour of the anti-theft alarm depends on the market.

Door switches

The door switches are mounted in the frame of the door concerned and grounded through the switch mounting screw to the bodywork. The switches are supplied with a pulse width-modulated (approx. 3.5%) voltage via a 1 kohm pull-up in TWICE. When a door is opened, the switch is closed and the control module input is grounded.

TWICE sends out information on the door position to the bus, where it is used by DICE, among others, for interior lighting. The anti-theft alarm also uses the door switch.

Switch, luggage compartment illumination

The luggage compartment switch is fitted in the tailgate lock. The switch is supplied with a pulse width-modulated (approx. 3.5%) voltage via a 1 kohm pull-up in TWICE. When the tailgate is opened, the switch is closed and the control module input is grounded.

TWICE sends out information on the tailgate position to the bus, where it is used by DICE for example for the luggage compartment lighting. The anti-theft alarm also uses the switch.

Key switch, luggage compartment disarm

The key switch is fitted by the boot lid and is grounded to the body. The switch is supplied with a pulse width modulated (approx. 3.5 %) voltage signal via a 1 kohm pull-up in TWICE. When the key is turned in the lock, the switch will close and ground the control module input. The boot lid is then disarmed.

Bonnet switch, anti-theft alarm

The bonnet switch is placed at the rear left of the engine bay. The switch is supplied with a pulse width-modulated (approx. 3.5%) voltage via a 1 kohm pull-up in TWICE. When the bonnet is opened, the switch is closed and the control module input is grounded.

TWICE uses the bonnet switch to trip the anti-theft alarm if the bonnet is opened when the alarm is armed.

Glass breakage sensor

The glass breakage sensor is located in the rear roof lamp (on the interior rear-view mirror on the Cabriolet) and is powered from TWICE.

The glass breakage sensor reacts to the sound of breaking glass. The sensor is of the active type and makes its own assessment and decision on whether the glass has been broken.

The sensor can be deactivated by pressing the NIGHT PANEL button on SID when the car key is not in the ignition. The glass breakage sensor is automatically deactivated on convertible cars when the soft top is lowered.

Tilt sensor

The tilt sensor is located in the centre console rear section and is powered from TWICE.

The sensor reacts to the car's angle and sets off the alarm if the car is raised on one side, just before the wheel is lifted off the ground.

It does not react for example if the car is buffeted by a strong wind. The sensor should however be disconnected if the car is to be transported on a ship as the anti-theft alarm can be tripped.

The sensor can be deactivated by pressing the NIGHT PANEL button on SID when the car key is not in the ignition.

Siren, anti-theft alarm

The siren unit is located at the rear edge of the left-hand front wheel housing. It has two piezo-electric sirens and is equipped with back-up batteries so that it will sound even if the ordinary car battery is disconnected or dead, or if somebody cuts the leads to the siren unit.

Direction indicators

The car's direction indicators are activated via bus information from TWICE which DICE uses to turn on the direction indicators.

LED, anti-theft alarm

The light emitting diode is located on top of the dashboard and is supplied with power from TWICE. (Only cars with theft protection have an LED.)

The LED is used to indicate the status of the anti-theft alarm:


- A double flash means that the car is immobilised.

- A flash every 3 seconds means that the anti-theft alarm is armed.

- A fast flash during the delay time means that a door or the bonnet or tailgate is open.

- A continuous light during the delay time means that everything is OK.


Remote control

The remote control is used to operate the central locking system of the car and to arm or disarm the anti-theft alarm. (Only cars with anti-theft alarm are equipped with remote control from the factory, may be retrofitted.)

The remote control has three buttons which have the following functions:


• Lock/arm anti-theft alarm

• Unlock/disarm anti-theft alarm

• Unlock tailgate/disarm anti-theft alarm on tailgate


When a button on the remote control is pressed, a code is sent to a receiver. The receiver is connected to TWICE which performs the required command.

P bus and I bus


On the Saab 9-3, only a few of the control modules are connected to any of the systems, compared with the Saab 9-5.

The two power-train systems, EDC and the diesel pump, are however not connected to the I bus. These systems require considerably faster communication so that no delays are noticeable, e.g. when EDC requests a certain fuel mass for injection.

Therefore, they are connected to a separate bus called the P bus (Power-train Bus). The data transfer rate on the P bus is ten times greater than that of the I bus.

The P bus is also connected to the MIU (Main Instrument Unit). The MIU is responsible for ensuring that information which is available on one of the buses is also made available on the other bus.