The antitheft alarm system (DWA) monitors the car for unauthorised access or intrusion. If an attempt is made to break into the car and enter the passenger compartment, an acoustic alarm in the form of a siren and a visual alarm via the lighting system are triggered.
The DWA electronics are integrated on the interior sensor control unit. They evaluate the signals relevant to the alarm system and decide whether the alarm should be triggered. The control unit is connected to the data bus K-CAN SYSTEM, across which it receives the signals of the door modules and CAS and power module control units. In addition, a separate DWA data bus is connected to the control unit, across which the signals between the DWA electronics and the control unit emergency siren/inclination sensor (SINE) are transferred.
The interior sensor monitors the vehicle interior using ultrasound waves. Movements in the vehicle interior are detected if the reflection of the ultrasonic waves (echo) change.
The interior sensor means that the vehicle interior is effectively protected against theft even if a window or the sunroof is open.
To prevent false alarms, the sensitivity of the interior sensor is adapted automatically. The following states influence the sensitivity:
The DWA-LED indicates the states of the antitheft alarm. It is activated directly by the DWA electronics across a wire. The following displays are possible:
The inclination sensor and the emergency siren are grouped as one component. They are linked to the DWA electronics across the DWA data bus.
The inclination sensor monitors the horizontal and vertical position of the vehicle and issues an alarm signal in the case of a position change.
The emergency siren emits an acoustic alarm if required. The alarm is triggered when the siren receives a corresponding command from the DWA electronics.
In addition, an alarm is triggered independently of the DWA electronics under the following conditions:
So that the emergency siren can operate independently of the vehicle battery, it is given a rechargeable battery that is charged when the engine is running.
In accordance with country-specific legislation, the emergency siren can be coded for an interval or intermittent tone.
In addition to the alarm trigger, the emergency siren can issue an acoustic acknowledgment signal on arming or disarming. This function can be coded in depending on country.
The Car Access System (CAS) control unit contains the functions of the radio remote control, the ignition switch, the terminal control and the immobiliser. It is also the gateway module between the data buses K-CAN SYSTEM and K-CAN PERIPHERALS.
The engine hood contact is connected at the CAS. This switch monitors opening of the engine hood. The switch status is sent across the data bus K-CAN SYSTEM to the DWA electronics.
In addition, the DWA control unit receives the following signals from CAS that are relevant to the alarm system:
The door modules register the signals of the switches and sensors installed in the doors and control the drives installed in the doors. Information is received and sent via the K-CAN PERIPHERALS data bus.
The following signals relevant to the alarm system are registered by the door modules and sent to the DWA electronics:
The power module monitors the battery charge level and the standby current consumption of the car. In addition, the boot lid lock is controlled via the power module. Information is received and sent via the K-CAN PERIPHERALS data bus.
The following signals relevant to the alarm system are registered by the power module and sent to the DWA electronics:
The light module controls and monitors the vehicle lights. Information is received and sent via the data bus K-CAN SYSTEM.
The light module evaluates the following information of the DWA electronics:
Locking/securing the central locking system arms the alarm system. (Note: Lock/secure assumes that, after switching off the ignition, before central locking, the driver's door has been opened and closed).
The DWA electronics send the command ”Arm” via the DWA data bus to the emergency siren/inclination sensor control unit. The emergency siren is then armed immediately.
Three seconds after arming, the door and lid contacts are included in the alarm monitoring, provided that the contacts are in idle state (doors and boot/bonnet closed).
As visual acknowledgement, the DWA LED begins to flash and the hazard warning system flashes once. Depending on the country version, the emergency siren can also issue a short sound signal.
After the antitheft alarm system has been armed and all doors, the engine hood and boot lid/tailgate have been closed, the interior sensor begins to scan the passenger compartment with ultrasound waves. After approx. 20 seconds, interior monitoring is possible. If the windows and/or the slide/tilt sunroof are closed using convenience operation, the interior scanning is interrupted.
In the same way as the interior monitoring, the inclination monitoring only begins after the doors and bonnet/boot have been closed. On receipt of the activation command, the inclination sensor a referencing procedure that takes 30 seconds. The inclination monitoring only begins after this period has elapsed.
The inclination and interior monitoring can be deactivated if a second central locking takes place within 10 seconds of the first central locking (e.g. pressing the central locking button on the remote control key twice).
Deactivation of the inclination and interior monitoring makes sense when the car is being transported (rail transport, ferry) and when animals or persons are left in the vehicle, or when the vehicle is parked in a duplex garage.
The DWA LED signals the deactivation by lighting up for 2 seconds.
The inclination sensor and interior sensor can also be deactivated using individual settings in the ”Configuration” menu of the on-board monitor.
After the antitheft alarm has been armed, the DWA electronics check the states of all the switches and sensors relevant to alarm monitoring (= alarm triggers). If a sensor is faulty or a switch is not in idle state (e.g. door or bonnet/boot open), this is not used for the alarm monitoring.
The DWA LED indicates by flashing for 10 seconds that an alarm trigger is faulty or not in idle state.
If an open door or bonnet or lid/tailgate is closed when the DWA is armed, the corresponding switch is set to idle state. The DWA then includes this switch in the alarm monitoring.
The DWA acknowledgement via the hazard warning system and (depending on country) via the siren only occurs when all alarm triggers are in idle state.
If the interior sensor, the inclination sensor or the DWA data bus are faulty, this is stored in the fault code memory.
Unlocking the driver's door or the passenger's door disarms the alarm system.
As visual acknowledgement, the DWA LED is switched off and the hazard warning system flashes twice. Depending on the country version, the emergency siren can also issue a short sound signal (double tone).
The alarm is triggered if an alarm trigger detects and alarm status when the antitheft alarm system is armed. The following states can be recognised:
Alarm trigger |
Alarm triggered by |
|---|---|
Door contacts |
Opening a door |
Boot lid contact |
Open boot lid |
Engine bonnet contact |
Opening the engine bonnet |
Interior sensor |
Motion in passenger compartment |
Inclination sensor |
Car on an incline |
Distribution switch (power module) |
Switch on distribution switch |
DWA data bus |
Break |
Vehicle voltage |
Voltage drop from 7.5 to 6.5 Volts within 40 minutes system voltage > 16 V |
If an alarm is detected, the DWA control unit activates the siren via the DWA data bus and sends an alarm message across the K-CAN SYSTEM data bus. The signal activates the visual alarm in the light module.
Independently of this, the alarm activated by the DWA electronics can trigger an acoustic alarm from the emergency siren if it is disconnected from the vehicle circuit through manipulation. If this also interrupts the DWA data bus, the visual alarm is also activated via the DWA control unit.
An alarm activated by the DWA electronics is cancelled immediately on disarming the antitheft alarm or by the signal ”Key in ignition” (from ZAS/CAS).
If the emergency siren reports a defect during the alarm or if the DWA data bus is interrupted, the acoustic alarm sounds on the fanfares. Here, the DWA electronics send a signal to the steering column switch cluster control unit.
The boot lid can be unlocked and opened using the remote control key without triggering an alarm even if the antitheft alarm is armed. Opening the boot lid deactivates the interior and inclination monitoring.
The interior and inclination monitoring are reactivated as soon as the boot lid is closed again.
The distribution switch is connected to the power module and it enables manual deactivation of various consumers required when the car is stationary. This enables the standby current consumption of the car to be reduced to a minimum during longer periods of immobilisation.
When the distribution switch is on, there is no alarm monitoring of the doors and bonnet/boot lid. The alarm monitoring of the remaining alarm triggers continues. The alarm monitoring in distribution mode can also be set individually in the ”Configuration” menu of the on-board monitor.
Switching on the distribution switch with the DWA armed triggers the alarm.
Crosswise operation enables arming and disarming of the antitheft alarm via the door lock operating location and the remote control key.
Insurance regulations in some countries mean that crosswise operation is disabled. If crosswise operation is omitted, the antitheft alarm can be armed using the door lock but not disarmed. Disarming is only possible using the remote control.
The crosswise operation function is coded in the Car Access System (CAS) control unit.
The alarm memory stores all the alarm messages that have led to a DWA alarm. The alarm memory is read out alongside the fault code memory.
The alarm messages registered by the DWA electronics are stored in the alarm memory of the component interior sensor with DWA electronics (DWA antitheft alarm).
For each alarm, the following supplementary information is also stored:
The alarms triggered by the emergency siren are stored in the fault code memory of the component emergency siren with inclination sensor (SINE emergency siren).
The following supplementary information is also stored:
Variations in road traffic regulations but also individual settings using the Car Key Memory can mean that the following different settings are present in the DWA electronics and the emergency siren:
Function |
Setting |
|---|---|
Acoustic acknowledgement via siren on arming and disarming |
Setting for USA/Canada |
Alarm tone |
In country-specific version ECE - interval sound In country-specific version USA/Canada intermittent (interrupted) sound |
Alarm duration of the acoustic alarm |
In all countries except Great Britain: 30 seconds In the Great Britain version: 5 minutes |
Visual alarm |
Via hazard warning lights in all countries Also full beam in USA/Canada Or dipped beam (not for xenon light) in other countries |