2000 BMW 540I SEDAN Owners Manual

185n
RepairsIndexOverview Controls Car care Technology Data

186n

Overview
Controls and features
Operation, care
and maintenance
Owner service procedures
Technical data
Index Advanced technology
187n
RepairsIndexOverview Controls Car care Technology Data
Airbags188
Adaptive Transmission Control
(ATC)188
Automatic Stability Control plus
Traction (ASC+T)/Dynamic
Stability Control (DSC)189
Radio reception190
BMW active seat190
Safety belt tensioner191
DSP sound system191
Interior rearview mirror with
automatic dimmer192
Rain sensor193
Tire Pressure Control (RDC)194
Integrated rear suspension194
Level control system195
Xenon lamps195

188n
Deceleration sensors continuously
monitor the physical forces acting upon
the vehicle. If, as the result of a frontal
collision, vehicle deceleration is
reached at which the protection of the
safety belts alone is no longer ade-
quate, the gas generators of the driver-
side and passenger-side airbags are ig-
nited simultaneously. However, the
passenger-side airbag is only triggered
if an additional sensor has recognized
that the passenger seat is occupied.
In the event of a side collision, the head
protection and side airbags in the front
and rear
* are triggered if necessary.
390de319
The airbags located under the marked
covers inflate and unfold in a matter of a
few milliseconds. In this process they
tear through the rated breaking points
of the upholstered covers or press them
out.
Because the inflation process must be
virtually instantaneous, it is necessarily
accompanied by a certain amount of
ignition and inflation noise. The gas
which the system employs to inflate the
airbag is not dangerous. Smoke
appears as the gas dissipates.
The entire process is completed within
fractions of a second.On vehicles with automatic transmis-
sion, Adaptive Transmission Control
(ATC) uses a number of factors to cal-
culate the gear which provides the
maximum efficiency. In this process it
monitors your personal driving style, the
situation in which you are driving, the
condition of the road and the traffic
conditions.
ATC recognizes your personal driving
style from the positions and movements
of the accelerator pedal, deceleration
when braking and lateral acceleration
through curves. Four different shift
characteristics Ð from comfort-oriented
to performance-oriented Ð are available
for selection by ATC.
390de334
ATC
Airbags ATC
*

189n
RepairsIndexOverview Controls Car care Technology Data
In order to take driving conditions into
account, ATC registers corners and
both uphill and downhill gradients. For
example, if you maintain speed through
a curve, the transmission does not up-
shift.
On uphill gradients, it shifts only when
the engine speed increases in order to
make more efficient use of power
reserves. On downhill gradients ATC
downshifts when the speed of the vehi-
cles increases, causing the driver to
step on the brakes.Precision sensors monitor the number
of revolutions of the wheels. When
equipped with DSC, they also monitor
steering angle, lateral acceleration,
brake pressure and the movement of
the vehicle around its vertical axis.
If differences in the wheel speeds
occur, the system counteracts the dan-
ger of wheelspin by reducing torque. If
necessary, the system also responds
with additional applications of the
brakes at the rear wheels.
If the system detects an instability in the
vehicle's condition, the braking action
can also be directed to help the front
wheels by the DSC in order to help sta-
bilize the vehicle.
You may need some time to become
accustomed to this system intervention.
However, it guarantees optimum drive
force and driving stability.
The braking intervention may be
accompanied by a certain degree of
noise.ATC
*
ASC+T/DSC
*

190n
Radio reception BMW active seat
*
AM provides substantially longer recep-
tion ranges than FM. AM broadcast
signals, propagated at ground level in
the form of surface waves, are also
reflected from the ionosphere as
atmospheric waves.
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
Although numerous factors combine
to impose inherent limitations on the
reception quality available from mobile
radios, specially designed systems can
be employed to minimize their effects:
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.
Because the ongoing antenna selection
process is completed within milli-sec-
onds, it remains inaudible to the radio
listener.BMW seats are configured for your
orthopedic well-being. The active seat
is an engineering enhancement of
BMW's seats, designed to ensure less
fatigue during extended trips while
sitting with little movement. The seat is
no longer a passive element between
the road, the running gear and the pas-
senger. Instead, it creates minor and
imperceptible shifts in your weight by
an active change in the contour of the
seat surface. The basic seat position is
not changed as this occurs.
Fluid cushions are located below the
surface of the seat in the seat's
upholstery on the left and right. The
fluid is circulated slowly back and forth
between the two cushions by means of
a pump. This causes a movement of the
spinal column which is nearly unnotice-
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191n
RepairsIndexOverview Controls Car care Technology Data
BMW active seat
*
Safety belt tensioner
able, resulting in an improved flow of
blood to the vertebral discs and the
muscles in the area of the spinal
column. Vehicle occupants can experi-
ence less muscle cramping, back pain
in the spine's lumbar region and fatigue.
The active seat thus provides a signifi-
cant contribution to your driving com-
fort and safety.
The 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 shoul-
der and lap belts within fractions of a
second. This reduces the tendency to
slide under the lap belt.
390de330

192n
DSP sound system
*
Interior rearview mirror with automatic dimmer
*
The DSP professional premium sound
system features a special amplifier
combined with Digital Sound Process-
ing (DSP) and integrated speakers to
surround you with crisp, true-to-life
sound reproduction.
The speaker system's subwoofers,
woofers, midrange speakers and tweet-
ers furnish you with an impressively full-
bodied listening experience. The indi-
vidual components are oriented so as
to produce the aural sensation that you
would experience facing the stage in a
concert hall. The system also automati-
cally adjusts the bass and treble set-
tings to compensate for changes in vol-
ume and vehicle speed.390de109
The interior rearview mirror with auto-
matic dimming feature reduces glare
from following traffic by adapting the in-
tensity of the reflected images to corre-
spond 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 of these sen-
sors is mounted on the front of the mir-
ror housing and is designed to monitor
light levels in the area immediately for-
ward of the vehicle. The second sensor
is integrated within the mirror's glass.
The electronic control system operates
by comparing the respective levels of
luminous intensity in front of and behind
the car. The difference provides the ba-
sic parameter used to modulate an
electrical current and induce chemical
changes in a semisolid layer incorpo-
rated in the lens.390de113
The semisolid reacts chemically to this
electrical current, thus providing infi-
nitely-variable dimming of the mirror
(electrochromic technology).
As a result, it is no longer necessary
to dim the mirror manually, and the
driver can maintain full concentration on
traffic.