Activate anti-theft alarm system, function

Function requirements, general

 C. 15C OFF

 Central locking (CL) functioning properly

Activate antitheft alarm system (ATA), general

The ATA is automatically activated with the CL when the vehicle is locked. Then the individual alarm inputs are monitored.

The activated ATA is indicated by an LED flashing permanently in the TS [AS] OFF switch and ATA function indicator (N72/1s27).

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The tow-away protection or interior protection (with code (882) Interior monitoring (only with ATA)) can be switched off before locking the CL.

 On vehicles for Belgium, the ATA arms automatically without locking the vehicle with the CL.

Activation of the ATA comprises several subfunctions:

 Function sequence for activating ATA

 Function sequence for switching off tow-away protection of ATA

 Function sequence for switching off interior protection of ATA
(with code (882) Interior monitoring (only with ATA))

 Function sequence for activating alarm inputs

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Function sequence for activating ATA

The partial function is comprised of the following subfunctions:

 Function sequence for locking CL with transmitter key (A8/1)

 Function sequence for locking CL with automatic relocking feature

 Function sequence for automatic activation (only on vehicles for Belgium)

 Special case: Driver door

If the driver door is still open when the CL is locked, it is not locked. When the driver door is closed, the alarm input is included in the check cycle. This leads to actuation of an alarm when opening the driver door without previous deactivation of the ATA. The status of the driver door is defined via the left front door contact switch (S17/3), whose status is read in directly by the rear SAM control unit with fuse and relay module (N10/2).

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Function sequence for locking CL with transmitter key

When the lock button on the transmitter key is actuated, it transmits a radio signal to the rear SAM control unit via the left antenna amplifier module 2 (A2/72).

The rear SAM control unit transmits a signal to the EIS control unit (N73) via the interior CAN. An infrared signal is transmitted to the left front IR receiver parallel to the radio signal (A26/1) (precise aiming required).

This signal is read in by the left front door control unit (N69/1) and transmitted to the EIS control unit via the interior CAN..

In both cases, the EIS control unit checks the access authorization of the transmitter key.

If the access authorization is valid, the message "Vehicle locked" is transmitted with the interior CAN to the SAM control unit, which then activates the ATA.

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Function sequence for locking CL with automatic relocking feature

The automatic relocking function is actuated by the EIS control unit. If the vehicle is unlocked and neither a door nor the liftgate is opened t = 40 s, the vehicle relocks automatically.

The EIS control unit transmits via the interior CAN the message "Vehicle locked" to the rear SAM control unit, which then activates the ATA.

The status of the left door is defined by the left front door contact switch, the status of the right door by the right front door contact switch(S17/4) and the status of the liftgate by the lock pawl rotary tumbler switch (S88/4). The signals from the contact switches listed are read in directly by the rear SAM control unit.

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Function sequence for self-activation

(only vehicles for Belgium)

When the transmitter key is removed from the EIS control unit, the driver door or the liftgate is opened and closed again, the ATA is activated automatically t = 2 s after closing, regardless of the status of the vehicle central locking.

The tow-away protection or interior protection (with code (882) Interior monitoring (only with ATA)) is switched to the same status as before opening.

Additional function requirements for switching off tow-away protection of ATA

 ATA not yet activated

Function sequence for switching off tow-away protection of ATA

Activation of the TS [AS] OFF switch with the ATA function indicator in the upper control panel control unit (N72/1) deactivates the tow-away protection for the following activation of the ATA.

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Deselection of the tow-away protection is confirmed by the ATA function indicator flashing in the TS [AS] OFF switch for approx.
t = 2 s after releasing the TS [AS] OFF switch.

Additional function requirements for switching off interior monitoring of ATA
(with code (882) Interior monitoring (only with ATA))

 ATA not yet activated

Function sequence for switching off interior protection of ATA

Activation of the IMS [IRS] OFF switch (N72/1s19) in the upper control panel control unit deactivates the interior protection for the following activation of the ATA.

Deselection of the interior protection by the LED flashing for approx. t = 2 s in the IMS [IRS] OFF switch at a frequency of
f = 6,25 Hz (t = 80 ms ON, t = 80 ms OFF).

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Additional function requirements for activating alarm inputs

 ATA activated

Function sequence for activating alarm inputs

The partial function is comprised of the following subfunctions:

 Function sequence for monitoring switch

 Function sequence for activating tow-away protection

 Function sequence for activating interior protection
(with code (882) Interior monitoring (only with ATA))

 Function sequence for activating alarm siren (H3/1)

Function sequence for monitoring switch

The status of the following switches is checked cyclically every
t = 0.5 s. If the polls indicate that an input is at rest within
t = 10 s, the corresponding input is then armed.

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Inputs set later to the non-actuated state, e.g. if the liftgate is closed only after the vehicle has been locked, are also armed
t = 10 s after closing.

Monitored switches:

- Left front door contact switch

- Right front door contact switch

- Engine hood ATA switch (S62)

- Pawl rotary tumbler switch

Function sequence for activating tow-away protection

The tow-away protection is activated if not previously deselected after t = 10 s after the closing command from the EIS control unit and after the last door or the trunk is closed. The ATA inclination sensor (B33) determines a reference position with which the relative vehicle inclination is compared during the activation time. Determination of this reference position requires approx. t = 10 s, therefore an alarm cannot be accepted before expiration of this time.

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The status of the ATA inclination sensor is read in and evaluated by the rear SAM control unit.

When the maximum vehicle inclination is exceeded with regard to the reference position, an alarm is triggered.

If the vehicle inclination changes very slowly (e.g. leaky tire), the reference position adapts to the current vehicle position to prevent inadvertent activation of the ATA inclination sensor.

If the vehicle ATA inclination sensor is faulty, all other components of the ATA continue to function properly and the corresponding fault codes are entered in the fault memory in the rear SAM control unit.

Function sequence for activating interior protection
(with code (882) Interior monitoring (only with ATA))

The interior protection is activated (if not previously deselected)
t = 10 s after the last door or the trunk is closed.

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The interior protection is ready for an alarm only after another
t = 20 s, because it is first necessary to calibrate the left interior protection transmitter/receiver unit (A26/4) to match the vehicle interior.

The status of the transmitter/receiver unit is monitored by the rear SAM control unit. If a defect is detected, the remaining ATA functions are still ensured regardless of this error. The corresponding fault codes are entered in the fault memory of the rear SAM control unit.

The rear window glass breakage sensor (B39/4) is monitored by the interior protection transmitter/receiver for open circuit.

Function sequence for activating alarm siren

The alarm siren is armed together with the ATA.

Communication between the rear SAM control unit and alarm siren is accomplished cyclically approx. every t = 700 ms.

 Deactivating ATA:

The ATA is deactivated completely by unlocking with the CL with the transmitter key via infrared or radio signal or by switching on c. 15C. The EIS control unit outputs the corresponding signal via the interior CAN to the rear SAM control unit which then activates the ATA.