BMW 3 (E46). Manual — part 225

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

the alarm system:

KL 30 (power)

KL 31 (ground)

STDWA signal (arm/disarm signal
from GM V)

NG signal (activate siren output
signal to the GM V)

The arm/disarm output signal from the
GM V (STDWA) is provided to the tilt
sensor, UIS sensor and the siren
simultaneously. The arm/disarm signal is
a switched ground that signals the
components of DWA armed/disarmed
status.

The activate the siren, the NG signal is
high whether DWA is armed or
disarmed. If a monitored input activates
the alarm, the high signal to the siren is
switched to a 50% duty cycle at the GM
V. The control circuitry in the siren
activates the siren. If the DWA is armed
and the battery is disconnected, the
siren circuitry recognizes the normally
high NG signal as suddenly going low.
In this case the siren is also activated.

Panic mode operation

When the trunk button on an FZV key is
pressed and held, the GM V activates
the siren for the panic mode. The panic
mode is functional with either an armed
or disarmed DWA system.

Emergency disarming

Emergency disarming occurs
automatically if a key is used to turn the
ignition switch ON and EWS accepts it.

The EWS signals the GM V to unlock the
doors and to deactivate the DWA.

520-1

General

This repair group covers removal and
installation of the front and rear seats.

Seat design and upholstery

The front seats installed in E46 cars
come in either manual or powered
versions. They offer firm support and
comfort. Their internal construction is
engineered to work together with the
vehicle suspension to absorb vibration.
The internal ventilation system of the
seats adds to the built-in comfort of
these seats.

Convertible front seats are unique to
those models in that they incorporate
the seat belts. This is called the Seat
Integrated Seatbelt (SGS) system.

Vinyl is the most common upholstery,
and leather is an available option. The
leather appears not only on the seats
but on the door panels and other areas
as well.

Front seatback nets are standard.

Seat adjustments

Regardless of level of trim, E46 seats
offer the following minimum
adjustments, with manual (photo) or
power controls (below):

Fore-aft position

Backrest angle