Antitheft and Alarm Systems: Description and Operation

Anti-Theft Alarm System

Anti-theft alarm system and sirens with tilt-alarm sensor
The anti-theft alarm system detects and indicates attempted intrusions and manipulation on the vehicle.
For the first time, the software for the alarm system and tilt sensor has been integrated into the emergency power siren (SINE = emergency power siren and tilt sensor). The SINE siren with tilt-alarm sensor is thus a control unit.
The passenger compartment is monitored using microwave sensors. Advantage: Microwave sensors can be hidden. Interior monitoring works also with open side windows, for example.
Any attempt to break into the vehicle and enter the passenger compartment triggers the alarm system. The DWA alarm is acoustic and visual.
The tilt sensor (integrated in the emergency power siren) monitor's the vehicle's angle of inclination. The tilt alarm sensor detects whether the vehicle is lifted or towed.







Brief component description
Descriptions are provided for the following alarm system components:

Microwave sensors
2 microwave sensors are installed on the interior door panels on \n driver and front passenger sides. 2 additional microwave sensors are mounted on the insides of the rear sections of the side panel.
The microwave sensors monitor the passenger compartment. Movement is detected if the reflection (echo) of the microwave changes. The sensitivity of the microwave sensors is adapted to various conditions (e.g. vehicle type, installation location of the microwave sensors).
A LIN bus connects each microwave sensor to the emergency power siren (SINE).







The microwave sensor is a motion detector. The microwave sensor detects any motion in any part of the vehicle's interior while also monitoring its direction (distance increases or declines).
3 seconds after the last door or lid closes, the microwave sensors initiate their reference run. The passenger compartment is scanned during the reference run. That enables changes in the passenger compartment to be detected (e.g. objects left lying on the rear seat). A self-test monitors that the microwave sensors operate correctly. 20 seconds after this reference run starts, the microwave sensors are operational.
The microwave sensors operate in a frequency range of approx. 2.5 GHz. These microwave sensors employ the Doppler effect (Christian Doppler 1803-1853) \n to generate the alarm trigger signal.
The interior monitoring system identifies the individual microwave sensors based on differences in their pin assignments.







SINE: Siren with tilt alarm sensor
The siren with tilt alarm sensor is installed in the right rear bumper.
The software for the alarm system is integrated in the emergency power siren. The SINE control unit in the emergency power siren controls the anti-theft alarm system. A LIN bus provides the connection between the microwave sensors and the SINE.
The SINE control unit is connected to the K-CAN2.







The emergency power siren issues the acoustic DWA alarm. As well as serving its alarm function, the emergency power siren can also emit a confirmation signal whenever the alarm system is armed and deactivated (can be programmed using the Central Information Display and Controller).
The SINE has its own voltage supply and also monitors the voltage supply in the battery. As a result an acoustic alarm can be emitted if the supply lead to the SINE is tampered with.
The SINE control unit also monitors the status of the earth wire and the LIN bus leading to the microwave sensors. Should any of these wires be cut the emergency power siren will also trigger the DWA alarm.
When the vehicle has been stationary for an extended period: The SINE does not trigger an anti-theft alarm when continuous discharge of the vehicle battery results in a drop of 0.5 volts per hour in the electrical system's voltage causes the system to fall to 3.0 volts.
The internal batteries revert to minimum power draw when the anti-theft alarm system is disarmed and no external power source is supplying the SINE. The power consumption in this instance does not exceed 25 microamperes. The SINE then reverts to its usual rate of power consumption once the vehicle battery is either reconnected or recharged.
The SINE detects a polarity reversal in the event of an external start and saves this in its information memory. The information memory, just like the alarm memory, can be read using the diagnosis system.
The tilt sensor monitors the position of the vehicle. This detects the vehicle being raised, for example to steal the wheels or tow the vehicle away. The vehicle parked position is stored using the current longitudinal angle and transverse angle. The tilt alarm sensor determines a new longitudinal angle and transverse angle every 90 milliseconds. If the threshold value is exceeded the SINE control unit will respond by triggering the anti-theft alarm. After a first alarm, the anti-theft alarm's threshold is lowered, which leads to a more rapid second alarm activation.
Whenever the vehicle is shaken, an internal counter is set to 0 as soon as a defined measured value is detected in the opposite direction to the first measurement. This prevents a false alarm from being triggered, even when the vehicle is being shaken vigorously.
The tilt sensor has diagnostic capability.

Engine compartment lid contact switch
The anti-theft alarm system relies on the bonnet's contact switch (engine compartment lid contact switch) to monitor the status of the bonnet (open or closed).
If the engine compartment lid is closed, then the contact in the engine compartment lid contact switch is open. If the engine compartment lid is opened, the state of the engine compartment lid contact switch changes (contact closed). The engine compartment lid contact switch is connected to the CAS control unit (Car Access System). The status of the engine compartment lid contact switch is evaluated by the CAS control unit. The CAS control unit transmits the status report to the siren and tilt alarm sensor via the K-CAN.
An engine compartment lid contact switch, that was not connected is evaluated by the Car Access System as closed. When the engine compartment lid is closed, the Car Access System receives a low signal.







Tailgate lock
The tailgate lock is equipped with the familiar rotary striker and interlock pawl closing elements.
The tailgate lock is electrically unlocked via the operating points. The JBE control unit operates the DC motor of the release drive unit in the boot/tailgate lock, thereby unlocking the boot/tailgate lock.
The status change in the rotary striker switch is also processed for the anti-theft alarm system. The electronics junction box transmits the status to the SINE control unit in the form of a message on the K-CAN2.







Door locks on driver's and front passenger's sides
The door lock is equipped with the familiar rotary striker and locking pawl to support its retention function. The door lock can be unlocked mechanically or electrically and then reopened.
A Hall-effect sensor is installed in each door-lock mechanism to serve as a door contact switch. The hall effect sensor detects whether the rotary striker is open or closed. Using the hall effect sensor signal, the footwell module (FRM) evaluates the status of the door contacts. The footwell module transmits the status to the SINE control unit in the form of a message on the K-CAN2. In addition to the door contact the driver's door lock also incorporates two additional Hall-effect sensors. Both these hall effect sensors are electronic lock contacts. The Hall-effect sensors monitor the position of the lock barrel in the driver's door (lock engagement and central deadlocking). This prevents accidental unlocking in response to random EMC interference (EMC = electromagnetic compatibility) and manipulated unlocking through targeted use of EMC interference.







Alarm system LED
The alarm system LED is at the bottom of the inside mirror. The alarm system LED visually indicates the statuses of the anti-theft alarm system.
The alarm system LED is directly activated using a wire from the DWA control unit in the emergency power siren. The following displays are possible:
- DWA LED off: DWA is disarmed.
- Alarm system LED flashes (flashing = 0.5 Hz): DWA is armed.
- Alarm system LED flashes (flashing = 2 Hz) for 10 seconds and then flashes: DWA has been activated but a door, the tailgate or the engine compartment lid has not been closed and/or a microwave sensor is faulty.
- Alarm system LED flashes for 5 minutes and then flashes: DWA anti-theft alarm.
- Alarm system LED lights up for 2 minutes and then flashes: The microwave sensors and the tilt sensor are deactivated.







System functions
The following system functions are described:
- Functional networking
- Activating and deactivating
- Triggering the DWA alarm (alarm trigger signal)
- Undervoltage detection, overvoltage detection, monitoring the battery (positive wire and negative lead)
- Monitors LIN bus
- Switching off the interior and tilt monitor
- Emergency function for the acoustic DWA alarm
- Crossover control by means of lock barrel and master key
- Panic mode in US and Japanese national versions

Functional networking
A complex system network with distributed functions residing in additional control units is needed to implement the anti-theft alarm system's functionality. The following illustration shows the functional networking.







Activating and deactivating
The anti-theft alarm system is armed when the locks are engaged and the deadlocking function activated using the central locking system. Conditions for lock engagement and central deadlocking are:
- The driver's door has been opened and reclosed since the power at Terminal 15 was switched off.
- The emergency power siren is then immediately activated.
- Three seconds after activation the door contacts and the contacts in the tailgate or the engine compartment lid are included in monitoring. It is required that the contacts are in rest state (doors and tailgate/engine compartment lid closed).
- The DWA LED begins to flash as a visual confirmation. The hazard warning flashers flashes once.
- Depending on the national-market version an acoustic signal from the emergency power siren can be emitted (see national-market version).
- After the DWA has been activated and all doors as well as the tailgate and the engine compartment lid have been closed, the microwave sensors begin to monitor the passenger compartment. After approx. 20 seconds, interior monitoring is possible.
- If the side windows and/or the slide/tilt sunroof are closed using convenience operation, the interior monitoring is interrupted.

In keeping with the interior monitoring, the tilt monitoring function also commences after the doors and lids/tailgate have been closed. After activating, the tilt alarm sensor first performs a reference run that takes 30 seconds. The tilt monitoring only begins after the reference run.
if the tailgate is opened during the reference run, the reference run is interrupted. After closing the tailgate, the reference run restarts. Those monitoring functions discharged by the microwave sensors and the tilt sensor assume priority. If a faulty door contact or contact in the engine compartment lid or the tailgate is detected, it is assumed that it is closed.
Unlocking central locking system deactivates the alarm system. As visual acknowledgement, the DWA LED is switched off and the hazard warning system flashes twice. Depending on the national-market version there may also be a supplementary brief signal (or two, depending on national version) from the emergency power siren. Even while the alarm system is armed, the remote control can be used to unlock and open the boot lid or tailgate without triggering the antitheft alarm system. When the tailgate is opened, the interior and tilt monitoring are disabled. The interior and tilt monitoring are reactivated as soon as the tailgate is closed again.

Triggering the DWA alarm (alarm trigger signal)
A DWA alarm is triggered if an alarm status is detected while the anti-theft system is activated. The following triggers a DWA alarm:
- Forced opening of a door: Bus signal from the electronics junction box (door contact switch)
- Forced opening of the tailgate: Bus signal from the electronics junction box (boot lid/tailgate contact switch)
- Forced opening of the engine compartment lid: Bus signal from the Car Access System (engine compartment lid contact switch)
- Movement within the passenger compartment: Signal from the microwave sensors
- Vehicle on an incline: signal from the tilt alarm sensor
- Line disconnection of the sub-bus (between DWA control unit in the emergency power siren and the microwave sensors)
- Undervoltage, overvoltage, monitoring the vehicle battery (positive wire and negative lead)

If a DWA alarm is triggered, the DWA control unit activates the speaker of the emergency power siren. Simultaneously the DWA control unit sends an alarm signal to the K-CAN. The footwell module activates the visual alarm via the lighting system. The emergency power siren can also trigger an acoustic alarm if it is separated from the vehicle electrical system through manipulation while the DWA is activated (independent voltage supply via batteries).
A DWA alarm is immediately cancelled under the following conditions:
- Disarming the antitheft alarm system
- Terminal 15 on

Undervoltage detection, overvoltage detection, monitoring the battery
Whenever DWA is activated, the DWA control unit monitors the vehicle voltage within a range of 6.5 and 17 volts. The DWA control unit detects the following deviations:
- Undervoltage: Vehicle voltage less than 6.5 Volts
- Overvoltage: Vehicle voltage greater than 17 volts
- Drop in the on-board supply voltage from 7.5 Volts to 6.5 Volts within 40 minutes
- Disconnecting the battery positive wire or the battery negative lead

The voltage thresholds for overvoltage and undervoltage must be detected for at least 250 milliseconds.

Monitoring the sub-bus for the anti-theft system
The sub-bus between the DWA control unit in the emergency power siren and the microwave sensor is monitored for line disconnection.

Switching off the interior and tilt monitor
Deactivating of the tilt and passenger compartment monitor makes sense under the following conditions:
- Transport of the vehicle (e.g. rail, ferry)
- Parking the vehicle in a two-level garage
- Leaving persons or animals behind in the vehicle

The tilt and interior monitoring systems are deactivated: when the "engage locks" and "deadlocking - engage central security system" commands are executed twice within a period of 3 seconds (for instance, with the remote control unit). The alarm system LED signals this disarming process by lighting up for 2 seconds.

Emergency function for the acoustic DWA alarm
The air horns provide the acoustic alarm if the emergency power siren fails while an alarm is being given or if the LIN bus link to the microwave sensors is interrupted. The SINE control unit also transmits a corresponding message to the steering column switch cluster (SZL).

Crossover control by means of lock barrel and master key
The antitheft alarm system can also be armed and disarmed via the remote control / master key (= crossover control). Due to insurance regulations, crossover control is prohibited in a few countries.
The anti-theft alarm system can be armed if the crossover control is not fitted, via the door lock, but cannot be disarmed using the door lock. Disarming is only possible using the master key. The crossover control function can be encoded in the Car Access System (CAS).

Panic mode in US and Japanese national versions
In the event of a threat from the outside or in the event of an accident, the panic mode can be used to attract the attention of others (DWA alarm). The panic mode must be programmed. In the US and Japanese national-market version, the tailgate release can be coded instead of panic mode. The tailgate release button then operates as panic mode button.
For this purpose, press the panic mode button for three seconds. The panic mode can be triggered regardless of the alarm system's status (armed or deactivated). Pressing any button on the master key terminates the panic mode. If the emergency power siren fails during panic mode, the acoustic alarm is output via the fanfares (emergency function). The duration of an alarm during panic mode is unlimited (until the battery is empty).

Notes for Service department

General notes

NOTICE: Note installation position of the emergency power siren.

Due to the fact that the tilt sensor is integrated in the SINE, great precision is required during installation of the emergency power siren.

Diagnosis instructions

Reading out the alarm memory
The most recent 10 DWA alarms are saved in the alarm memory of the DWA control unit. The alarm memory is read out together with the fault memory. Each time an antitheft alarm is triggered the following supplementary information is also stored:
- Alarm trigger signal with history
- Date and time display
- Ambient temperature

The last 5 antitheft alarm triggering events are stored in the microwave sensors' alarm memory. Each time an antitheft alarm is triggered the following internal information is also saved:
- Alarm trigger signal (overvoltage, undervoltage, line disconnection [open circuit], short circuit)
- Ambient temperature

NOTICE: Check charge status of the batteries in the emergency power siren.

The charge status of the internal batteries in the emergency power siren can be accessed using the diagnosis tool.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.