Alarm Siren - BMW 1999-2005 M3 Service Manual

Central Locking and Anti-Theft
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The module operates in pulse mode.
The radar unit transmits a signal, then
pauses for the reflected signals to be
received by the module.
The detection range of the radar is
adjusted by rapid switching when the
system is armed. This allows the sensor
to adjust its range to either the
windshield with the top lowered or to the
soft top when it is raised.
The module will signal the GM V to
trigger the alarm if a new object is
detected within its sensing hemisphere.
However, false alarms may be triggered
by objects falling into the interior when
the system is armed with the top
lowered. Also, large metal objects, such
as the seat backrests, will shield the
microwave pulse and create a sensor
"shadow" effect in the interior.
As with the tilt sensor and the UIS, the
SDR sensor can be switched OFF by
activating the central locking system
twice within 10 seconds.

Alarm siren

The DWA siren is installed in the right
rear engine compartment. This location
provides a secure position with loud
acoustic output.
The siren contains electronic circuitry for
producing the warning tone when the
alarm is triggered. The siren also
contains a rechargeable battery that is
used to power the siren when the alarm
is triggered. The rechargeable battery
will allow the siren to sound if it or the
vehicle battery is disconnected. The
siren battery is recharged from the
vehicle battery when DWA is not in the
armed state.
The siren has four wires connecting it to
2/25/2009 11:00 PM