BMW 320i 2001 Owners Manual

181n
IndexDataTechnologyRepairsCar careControlsOverview
Radio receptionThe AM frequency bands (medium-
wave, long-wave and short-wave) make
it possible to receive stations from a
great distance, because the broadcast
signals travel not only along the ground
as surface waves, but also as
atmospheric waves that are reflected
from the ionosphere.
Frequency-modulation (FM) provides
substantially better sound quality than
AM. However, because FM transmis-
sions rely on line-of-sight broadcast
waves, their effective reception range is
limited. 360de084
The limitations inherent to radio recep-
tion in a moving vehicle have been
minimized by a number of innovative
system designs:
The "Radio Data System" (RDS) makes
sure that, for broadcast stations
sending on several frequencies, the
radio automatically tunes to the
frequency with the best reception
quality.
The Diversity Antenna system employs
several FM antennas integrated within
the rear window to provide three sepa-
rate sources for receiving broadcast
waves. An integral processor automati-
cally selects the antenna with the best
FM reception quality at any given time.
The selection of the antenna takes
place within milliseconds, and is there-
fore not noticed by the radio listener.

182n
Four-wheel driveThe transmission of power to the four
drive wheels is provided permanently
through a transfer box. The distribution
of torque between the front and rear
axles is 38% to 62%.
Traditional differential locks at the front
and rear axles and in the transfer box
are not required. Their function is taken
over by automatic braking intervention
at all four wheels. These traction inter-
ventions are governed by Automatic
Differential Brake (ADB-X), a sub-func-
tion of DSC.
If a wheel tends to slip, it is braked
automatically by ADB-X until it once
again gains traction, and drive force
can be transmitted to that wheel. In
addition, the drive force is distributed to
the remaining wheels during this 530us133
system intervention. Engine output is
also reduced if necessary.
When the DSC is deactivated, the
ADB-X traction intervention is set for
the maximum drive force. However, the
engine intervention and the stability
controls are no longer available. For
this reason, DSC should only be deacti-
vated in the exceptional circumstances
described on page 84.
The BMW 325xi and 330xi are not
intended for off-road operation. But the
permanent four-wheel drive provides a
high degree of driving stability and trac-
tion on all road conditions and surfaces.
It supports you in critical driving condi-
tions, e.g. in extreme winter conditions
or on loose road surfaces.

183n
IndexDataTechnologyRepairsCar careControlsOverview
Safety belt tensionerThe safety belt tensioner responds to
severe frontal collisions by tightening
the belts to ensure that occupants
remain firmly positioned in their seats.
A gas-pressure system retracts the
buckle assembly to tension the
shoulder and lap belts within fractions
of a second. This further reduces the
tendency to slide under the lap belt. 390de330

184n
Interior rearview mirror with automatic dimming feature
*
The interior rearview mirror with auto-
matic dimming feature reduces blinding
from following traffic by adapting the
intensity of the reflected images to
correspond to levels of light registered
by the unit's sensors. The mirror reverts
to its undimmed setting as soon as the
light source disappears. One lamp
sensor is mounted on the front of the
mirror housing. This sensor, which is
directed forward, measures light inten-
sity in the area ahead of the vehicle.
The second sensor is integrated within
the mirror's glass. The electronic
control system compares the light
intensity from front and rear. The differ-
ence provides the basic parameter
used to modulate an electrical current
and induce chemical changes in a
semisolid layer incorporated in the lens.463us013
The semisolid reacts chemically to this
electrical current, thus providing
dimming of the mirror through an infi-
nitely-variable range (electrochromic
technology).
As a result, it is no longer necessary to
dim the mirror manually, and the driver
can concentrate completely on traffic
conditions.

185n
IndexDataTechnologyRepairsCar careControlsOverview
Rain sensor
*
Depending on the degree of wetness
on the windshield, the rain sensor
controls the operation of the windshield
wipers.
Infrared light is carried along the
surface of the windshield in an optical
conductor in such a manner that it is
reflected completely when the wind-
shield is dry. The quantity of reflected
light is measured.
If there is moisture on the glass, the
amount of light reflected is reduced
since the infrared light at the surface of
the windshield can escape. The quan-
tity of reflected light is thus a means of
gauging the degree of wetness on the
windshield.390de133
When the system is set to the "Intermit-
tent" wiper speed, the wipers react
immediately Ð if water is splashed onto
the windshield by vehicles traveling
ahead of you, for example. As a result,
the rain sensor provides a contribution
to driving safety and comfort.

186n
Tire Pressure Control (RDC)
*
This system regularly checks tire pres-
sure and monitors all four tires even
while driving, so you don't have to.
Behind the valve stem in every wheel,
there is an electronic chip that is
designed for severe-duty applications
and long service life. It contains a pres-
sure sensor, a transmitter and a battery.
The pressure is measured in extremely
short time intervals and then transmitted
by a radio signal. If an irregularity is
detected, the transmission rate is
increased. 460de169
Near every wheel is an antenna in the
body that receives the signal from the
wheel. A central electronics system
evaluates the quadruple signals and
forwards any changes.
The RDC provides an important contri-
bution to driving safety.

187n
IndexDataTechnologyRepairsCar careControlsOverview
Self-diagnostics All of the important electrical and elec-
tronic systems in the vehicle are tested
regularly and automatically Ð the driver
does not have to perform any extra
operations or adjustments.
The indicator lamps also come on
briefly after the ignition has been turned
on.
While you are driving, the functional
status of the actuator motors (for the
windshield wipers, power windows,
seats, sliding/tilt sunroof, etc.) is
constantly analyzed by current
measurements in their relays.460de177
In the same manner, the electrical
resistance of the airbag ignition genera-
tors and all of the remaining airbag
components is measured at all times.
Any fault in this system would be
detected immediately by a current fluc-
tuation that would necessarily accom-
pany it. The fault would be indicated
immediately by the airbag warning
lamp.
Even after you shut off the engine, the
overall functional status of your vehicle
is monitored. For example, all of the
flaps of the heating and ventilation
system travel to the nearest limit posi-
tion. This ensures that the defrost func-
tion is always available even if a
malfunction in the air conditioner
system/automatic climate control
should occur while the vehicle is
parked overnight, for instance.
A calibration cycle runs every tenth time
the engine is shut off. During this cycle,
the actuator motors of all the heating
and ventilation flaps travel to their limit
stops in both directions. The limit posi-
tions and the return travel paths are
checked in this manner in order to
ensure that appropriate adjustments for
the operating elements can be made at
any time.You will hear the sounds of the air flaps
as the air conditioning system/auto-
matic climate control carry out their
self-diagnostic functions after the igni-
tion has been turned off. All of the other
self-diagnostics functions operate
silently in the background.
Any possible faults detected during
these self-diagnostics can be read out
by your BMW center during the next
regularly-scheduled maintenance and
corrected with a minimum of time.

188n
Xenon lamps
*
The xenon lamp provides forward illu-
mination with significantly more bright-
ness and uniformity than the traditional
halogen lamp.
In a xenon lamp, an electric arc replaces
the filament in order to generate intense
illumination. A gas mixture in a quartz
glass tube with metal vapor is ignited by
a high electric voltage. The arc that is
generated is then sustained by a lower
voltage. When the lamp is turned on,
there is a brief warm-up period.
Maximum brightness is attained in
approx. 15 seconds.390de134
Xenon lamps provide significantly-
improved visibility, especially during
adverse weather conditions and driving
situations, (driving at night in heavy rain
or through road repair areas where
there are no lane markers, for instance).
Vehicles with xenon lamps are
equipped with automatic headlamp
range control. As a result, the lane
ahead of you is always optimally
lighted, even under varying load condi-
tions, and drivers in oncoming traffic
are not blinded.
Xenon lamps make a significant contri-
bution to highway safety since other
highway users, bicyclists and motorcy-
clists in the right lane, and pedestrians
are more easily detected.

189n
IndexDataTechnologyRepairsCar careControlsOverview

190n