Double flashing

Double flashing indicates that the alarm system is activated but has not reached a state of full operational readiness.

Possible reasons are:

- The system has been activated by three times rapidly locking a door because e.g. the central locking is not functioning properly.

- During the off-time at least one triggering circuit is not in order

(e.g. glove compartment open). The alarm system is then activated without monitoring this input.

- An alarm has been triggered at least once. Both during and after the alarm the LED's double-flash.

Alarm triggering

As soon as the alarm system passes into activated mode, an alarm can be triggered by each of the inputs below, provided that input is in order.

This takes place due to an alteration of the input signal.

The following inputs are monitored;

• Triggering via ground contact

- Door contacts

- Engine hood contact

- Luggage compartment contact

- Radio contact 2

- Glove compartment contact

- Central locking (microswitch)

- Additional sensors 1 and 2

• Triggering via plus contact

- Ignition lock terminal 15

- Central locking (microswitch)

- Additional sensors 3

• Triggering via disconnection of a closed circuit loop

- Radio contact 1

If the alarm-triggering contact is again in order (Including 10 second off-time) the contact can once again trigger an alarm.

Type of alarm

The alarm can be one of three types specifically prescribed for each country and pre-set at the factory.

If an alarm control unit is replaced, system tester 9288 must be used to input the correct coding for the country concerned.

Depending on the coding, the alarm is indicated, when triggered, by:

- Alarm horn

- Turn signals

- Interior light

If the alarm system is switched off via the door locks all alarm action is interrupted immediately. Anti-theft feature

When the alarm system is activated the anti-theft feature works by interrupting the ignition (terminal 15):

For safety reasons the anti-theft feature is not activated if one of the following conditions is met:

- the alarm system Is switched off

- the vehicle speed is greater that 10 km/h (6 mph)

- terminal 61 registers regulated voltage


Two kinds of faults can occur:

Faults which render the alarm system inoperative and faults which merely limit its effectiveness, e.g. defective inputs during off-time, which are then not monitored.

Every fault is stored in the control unit and can be called up during diagnosis.

An interruption of the power supply when the alarm is activated is recognized as a fault. If the system was activated beforehand, it reverts to activated mode once the interruption has been eliminated. The stored fault data remain unaffected.

Faults in the central locking system can be bypassed by locking the door rapidly three times so as to activate the alarm system.

By means of appropriate bounce-pulse blocking times of approx. 100 ms (contact chatter) of the alarm contacts, interference pulses are not recognized as a change of level (thereby causing accidental triggering of the alarm).

Central locking

The central locking is activated via the door key. Therefore the central locking button on the center console can only lock the doors when the ignition key is removed.

With the ignition on, the central locking button can both lock and unlock the doors. In addition the locking mechanism can be activated via the door knobs or rotary knobs on the doors. A knob can unlock both doors but only lock one side.

If the command to lock is given when the driver's door is open, a mechanical anti-locking device prevents the driver's door from being locked, and the central locking is unlocked.

The indicator lamp in the locking button lights up if at least one door is locked when the "ignition on" position is reached.

To avoid overloading the actuating motors when the central locking is activated frequently in rapid succession, a protective device switches off the actuation signal to the motors for approx. 20 seconds.

Interior light delay

The alarm control unit also takes over the delayed switch-off function of the interior lights (delay time approx. 20 seconds).

If the ignition is switched off when the doors are opened, the switch-off delay time starts when the doors are closed.

The interior lights remain on for approx. 20 seconds unless the ignition is switched on or one of the doors is locked first.

The delay time is not started by closing of the tailgate.


The alarm control unit is diagnosis-compatible and can be diagnosed using system tester 9288. The menu comprises the following function groups:


l=Fault memory


3=Switch inputs


< Menu l=Country code 2=Faults 3=System check

1 = Fault memory

The fault memory consists of an inversible memory (EEPROM), i.e. if the power supply is interrupted any information stored will be retained and must be erased deliberately once the fault has been eliminated. A maximum of 12 faults can be stored simultaneously.


For some of the faults designed to be stored, it should be remembered that there are two possibilities:

1. The fault indicated is a genuine fault which must be eliminated.

2. The fault indicated is a fault condition, e.g. if the glove compartment is accidently left open {with the alarm activated).

Possible faults or fault conditions of the alarm system fnnl-ml nr i f

Voltage failure Term. 3 0 with active Alarm system present

Voltage failure during

Alarm output present

Position of drivers implausible present



when activaiting open

Luggage comp. when activaiting open

Engine comp, when activaiting open r

Glove comp, when activaiting open

Possible faults or fault conditions of the alarm system

Input 2

when activaiting to ground


(closed cirr. loop) when activaiting interrupted

Centr. lock button when activaiting closed

Radio contact when activaiting to ground

Input 1

when activaiting to plus

Tailgate lock switch when activaiting closed

Input 3 3

when activaiting activation

Position switch on drive when activaiting closed

Position switch on drive when activaiting open

2 = Drive links

With the function "Drive links" it is possible to activate the following components using system tester 9288.

Drive links 1= Function display 2= Locking 3= Alarm horn

<Drive links 1= Indicators 2= Interior light 3= Warning lamp

<Drive links 1= External output 2= Anti-dr.-off feat.

3 = Switch inputs

With the function "switch inputs" it is possible to check all the contacts of the alarm system


Menu display 2

< Menu l=Country code 2=Faults 3=System check

1 = Country code

Due to different legislation in different countries it is possible to code three prescribed alarm variants using system tester 9288.

Alarm code German market

- Alarm horn max. 30 seconds intermittent Horn frequency = 2.5 Hz

- Indicators max. 5 minutes Flashing frequency = 2.5 Hz

- Interior lights flashing asynchronously with indicators

Alarm code Swiss market

- Alarm horn max. 30 seconds constant

Alarm code US market

- Alarm horn max. 4 minutes intermittent Horn frequency = 2.5 Hz

- Indicators max. 8 minutes Flashing frequency = 2.5 Hz

- Interior lights flashing asynchronously with indicators

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