Activate anti-theft alarm system, function

Function requirements, general

 Circuit 15 Off

 Central locking operating properly

Activate antitheft alarm system (ATA), general

The antitheft alarm system (ATA) is activated automatically when locking the vehicle with the central locking (CL); then the individual alarm inputs are monitored. The activated ATA is indicated by an LED flashing permanently in the TS OFF switch (N72/1s18) at a frequency of f = 1 Hz.

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

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 It is possible to switch off the tow-away protection or on vehicles with code (882) Interior monitoring (only with ATA) the interior protection feature before locking 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

 Function sequence for activating alarm inputs

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Function sequence for activating ATA

The function sequence for activating the ATA comprises the following subfunctions:

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

 Function sequence for locking CL with automatic relocking feature

 Function sequence for self-activation (Belgium only)

Function sequence for locking CL with transmitter key

When the lock button on the transmitter key is actuated, it transmits a radio signal via the central locking antenna (A2/34) to the SAM control unit (N10). It relays a signal to the ATA/tow-away protection/interior protection control unit (N26/6) via the interior CAN.

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On model 169.3 with code (583) Two front power windows with convenience feature or model 169.0 and model 245.2 with code (584) Two rear power windows an infrared signal is transmitted parallel to the radio signal to the left front IR receiver(A26/1) (precise aiming required). 'This signal is read in by the left front door control unit (N69/1) and transmitted to the ATA/tow-away protection/interior protection control unit via the interior CAN.

In both cases, the EIS control unit (N73) 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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Special case: Driver door

If the driver door is still open when the CL is locked, it is not locked. After the driver door is closed, the door status is transmitted to the ATA/tow-away protection/interior protection control unit by the left front door control unit via the interior CAN. . The alarm input is then included in the check cycle. This leads to actuation of an alarm when opening the driver door without previous deactivation of the ATA.

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 trunk lid is opened within 40 s, the vehicle relocks automatically. The EIS control unit transmits via interior CAN the message "Vehicle locked" to the rear SAM control unit, which then activates the ATA.

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Function sequence for self-activation (Belgium only)

When the transmitter key is removed from the EIS control unit, the driver door or the trunk lid is opened and closed again, then the ATA is activated automatically 2 s after the last door or the trunk lid is closed, regardless of the status of the vehicle central locking.

The interior protection and the tow-away protection are set to the same state as before the last unlocking procedure.

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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

The TS OFF switch in the upper control panel control unit (N72/1) is read in via the local interconnect network (LIN) by the automatic heater control and operating unit (N18) (without code (580) Automatic air conditioning and without code (581) Comfort automatic air conditioning) or AAC operating and control unit (N22) (with code (580) Automatic air conditioning) o comfort AAC operating and control unit (N22/7) (with code (581) Comfort automatic air conditioning). It transmits the signal to the ATA/tow-away protection/interior protection control via the interior CAN. From there, the tow-away protection is deactivated after the ATA is activated. Deselection of the tow-away protection is confirmed by the LED in the TS [AS] OFF switch coming on for approx. t = 2 s after releasing the TS [AS] OFF switch.

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Additional function requirements for switching off interior protection of ATA

 ATA not yet activated

Function sequence for switching off interior protection of ATA

The IRS OFF switch (N72/1s19) in the upper control panel control unit is read in by the automatic heater control and operating unit or AAC operating and control unit o comfort AAC operating and control unit via LIN. It transmits the signal to the ATA/tow-away protection/interior protection control via the interior CAN. From there, the interior protection is deactivated after the ATA is activated. Deselection of the interior protection is confirmed by the function indicator flashing for approx. t = 2 s in the IRS OFF switch at 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 function sequence for activating alarm inputs comprises the following subfunctions:

 Function sequence for monitoring alarm inputs

 Function sequence for activating tow-away protection

 Function sequence for activating interior protection

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

 Function sequence for deactivating ATA

Function sequence for monitoring alarm inputs

The status of the following switches or alarm inputs is checked cyclically every t = 200 ms. If the polls indicate that an input is at rest within t = 10 s, the corresponding input is then armed.

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

The ATA evaluates the following alarm inputs:

- Alarm signal siren

- Right front door rotary tumbler microswitch (M14/5s1)

- Left front door rotary tumbler microswitch (M14/6s1)

- Rear-end door rotary tumbler microswitch (M14/7s1)

- Left rear door rotary tumbler microswitch (M14/8s1)
(on model 169.0, 245.2)

- Right rear door rotary tumbler microswitch (M14/9s1)
(on model 169.0, 245.2)

- Engine hood ATA switch (S62)

The status of the left front door rotary tumbler microswitch is read in by the left front door control unit and the status of the right front door rotary tumbler microswitch is read in by the right front door control unit (N69/2) and transmitted to the ATA/tow-away protection/interior protection control unit via the interior CAN.

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The status of the left and right rear door rotary tumbler microswitch is read in:

- On model 169 and model 245.2 without code (584) Two rear power windows directly by the SAM control unit.

- On model 169.0 and model 245.2 with code (584) Two rear power windows by the left rear door control unit (N69/3) and right rear door control unit (N69/4) .

The status of the rear-end door rotary tumbler microswitch is read in directly by the SAM control unit and the status of the ATA engine hood switch is read in directly by the ATA/tow-away protection/interior protection control.

Function sequence for activating tow-away protection

The tow-away protection is activated automatically (it not previously deselected for the next locking operation) t = 10 s after the locking command from the EIS control unit and after closing the last door or the trunk lid.

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The ATA inclination sensor integrated into the ATA/tow-away protection/interior protection control unit determines the reference position with which the relative vehicle inclination is compared during the activated time. Determination of this reference position requires approx. t =
10 s, therefore this arming operation must be completed before an alarm can be triggered.

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 ATA inclination sensor is defective, all other components of the ATA remain operable.

If the system is faulty, the corresponding error codes are entered in the fault memory of the ATA/tow-away protection/interior protection control.

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Function sequence for activating interior protection

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

The interior protection is ready for an alarm only after another t = 30 s, because the ultrasonic sensor integrated into the ATA/tow-away protection/interior protection control unit first has to calibrate to the vehicle interior. The status of the ultrasonic sensor is monitored by the ATA/tow-away protection/interior protection control.

If a defect is detected, the remaining ATA functions are still ensured regardless of this error.

The corresponding fault codes are stored in the fault memory of the ATA/tow-away protection/interior protection control.

Function sequence for activating alarm siren

The alarm siren is armed together with the ATA approx. every t = 400 to 900 ms and checked cyclically by the ATA/tow-away protection/interior protection control via a direct line.

If the ATA/tow-away protection/interior protection control unit does not receive an answer within approx. t = 1 s from the alarm siren, an alarm is triggered. The alarm is only output visually, as the alarm signal horn cannot be addressed

If the alarm siren detects the loss of the power supply or the communication it automatically outputs an acoustic alarm.

Function sequence for deactivating ATA

The ATA is deactivated by opening the CL with the transmitter key via infrared or by inserting a valid transmitter key into the EIS control unit. The EIS control unit transits the corresponding signal via the interior CAN to the ATA/tow-away protection/interior protection control, which then deactivates the ATA.