Anti-theft alarm system trigger, function

General function requirements

 Anti-theft alarm system (ATA) activated

ATA alarm triggering, general

If one of the alarm inputs of the activated ATA exits its non-actuated state, an alarm is triggered.

 Alarm actuation in the event of undervoltage

The operating voltage of the ATA is defined from
U = 8.5 V to U = 15.5 V. If the voltage drops below
U 8,5 V, it is no longer possible to trigger a visual alarm output. Only an acoustic alarm is triggered. The battery voltage is stored in the ATA alarm memory in the rear SAM control unit with fuse and relay module (N10/2).

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The ATA alarm triggering comprises the following subfunctions:

 Function sequence for alarm triggering by opening a door, tailgate or engine hood

 Function sequence for alarm actuation with tow-away protection

 Function sequence for triggering alarm by interior monitoring
(with code (882) Interior monitoring (only with ATA))

 Function sequence for alarm actuation from communication loss to alarm siren (H3/1)

 Function sequence for alarm output

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Function sequence for alarm triggering by opening a door, tailgate or engine hood

The rear SAM control unit actuates an alarm as soon as the non-actuated state of one of the following contact switches is interrupted for t > 0.5 s:

- Left front door contact switch (S17/3)

- Right front door contact switch (S17/4)

- Engine hood ATA switch (S62)

- Pawl rotary tumbler switch (S88/4)

Opening the left door is recognized by the left front door contact switch, opening the right door by the right front door contact switch.

The ATA engine hood switch recognizes if the engine hood is open, the locking pawl rotary tumbler switch if the liftgate is open.

The status of the contact switches listed is read in directly by the rear SAM control unit. For a new alarm actuation, the corresponding contact switch must first change to the non-actuated state (debounce time t = 500 ms).

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After a non-actuated state of t = 10 s an alarm can be reactuated by the same contact switch, if an acoustic alarm is not present.

 If a locked vehicle is unlocked with the mechanical key and the door is opened, the rear SAM control unit triggers an alarm.

Additional function requirements for alarm actuation by tow-away protection

 Tow-away protection not deactivated

 Changing vehicle inclination (in relation to horizontal axis) from = 3 to 3.5° at a change rate of
1  0,5° pro min

Function sequence for alarm actuation with tow-away protection

If the ATA inclination sensor (B33) recognizes an alarm-relevant inclination motion, an alarm is output.

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

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 Alarm is recognized before a wheel looses ground contact when lifting the vehicle.

Additional function requirements for alarm actuation by interior monitoring
(with code (882) Interior monitoring (only with ATA))

 Interior protection not deactivated

Function sequence for triggering alarm by interior monitoring

The vehicle interior is monitored by the left interior protection transmitter/receiver unit (A26/4).

An open circuit in the rear window glass breakage sensor (B39/4) is recognized and evaluated by the interior protection transmitter/receiver unit. If the events are recognized as alarm-relevant, the interior protection transmitter/receiver unit transmits a corresponding signal to the overhead control panel control unit (N70), which relays a signal to the rear SAM control unit via the interior CAN. The rear SAM control unit initiates an alarm.

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Function sequence for alarm actuation from communication loss to alarm siren

Communication between the rear SAM control unit and alarm siren is accomplished cyclically approx. every t = 700 ms. If the alarm siren does not receive a communication request from the rear SAM control unit within t = 1 s, an acoustic alarm is output. If communication does not take place between the alarm siren and the rear SAM control unit, a visual alarm is output.

If the alarm siren detects a loss of power resulting from disconnecting the connection lines or the battery (G1), it outputs an acoustic alarm automatically.

 An alarm is only repeated if a new alarm event is registered after the acoustic alarm was terminated.

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Function sequence for alarm output

The visual alarm is output by the vehicle exterior lights. The following components are actuated:

- By the front SAM control unit with fuse and relay module (N10/1)

- Left turn signal lamp (E1e5)

- Right turn signal lamp (E2e5)

- By the rear SAM control unit:

- Left turn signal lamp (E3e1)

- Right turn signal lamp (E4e1)

- By left front door control unit (N69/1):

- Left outside mirror turn signal lamp (E6/5)

- By right front door control unit (N69/2):

- Right outside mirror turn signal lamp (E6/6)

The acoustic alarm is output by actuating the alarm siren in the rear SAM control unit.

The overhead control panel control unit switches on the interior illumination.

An activated alarm is interrupted under the following conditions:

- Unlocking central locking (CL) with transmitter key (A8/1)

- Switching on c. 15C
(transmitter key is inserted into EIS control unit (N73))

The EIS control unit transmits the corresponding signal via the interior CAN to the rear SAM control unit, which then terminates the activated alarm.