sensor AUDI S8 2009 Service Manual

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& WARNING
Changing the vehicle's su spension includ ing use of un approved
tire -rim combinations can change Advanced Airbag performance
and increase the ris k of serious personal injury in a crash .
• Never install suspen sion component s that do not have the
same performance chara cteristics as the components or iginally
installed on your vehicle.
• Never use tire-r im comb inations that have not been approved
by Audi.
& WARNING
Items stored between the safety belt bu ckle and the center
c onsole can cause the sensors in the buc kle to send the wrong
information to the electroni c control module and prevent the
Advanced Airbag System from working properly .
• Alway s make sure that nothing can interfere with the safety
belt buckles and that they are not obstructed .
<£> For the sake of the environment
Undeployed airbag modules a nd pretensioners might be classified
as Pe rchlorate Mat erial -spe cia l han dling may a pply, see
www.dtsc.ca.gov/hazardouswaste/perchlorate. When the vehicle or
par ts o f the restraint syst em i ncludi ng ai rbag modules and saf ety
belts with pretensioners are scrapped, a ll app licab le laws and regu­
latio ns must be observed . Yo ur au thori zed A udi dealer is fam ilia r
with these requirements and we recommend that you have your
dealer perfo rm this serv ice for you .•
Knee airbags
Description of knee airbags
T he airba g sys tem c an prov id e sup plemen tal prot ect ion
t o pro pe rly rest rained fron t seat occ upant s.
0
Fig. 2 36 Drive r's
airba g
The airbag for the driver is located in the instrument panel under ­
neath the steering wheel=> fig. 236, the airbag for the passenger is
at about the same height in the instrument panel und erneath the
glove compartment.
T he knee air bag offe rs addi tio nal pr ote cti on to the d river's a nd
passenger 's knees and upper and lower thigh ar eas as a supple ­
me nt to t he sa fety be lts.
I f the front airbags deploy , the knee airbags also deploy in frontal
collisions above a certain severity=> page
229, "M ore important
thi ngs to kno w about fron t a irba gs" .
B esides their normal safety function, safety belts wor k to help keep
t h e dri ver o r fr on t passeng er in pos itio n in case of a fro ntal col lis ion
so that the airbags can provide protection .
T he airbag system is not a substitute for your safety belt . Rathe r, it
i s part of the overa ll occupa nt res tra int system i n your ve hi cle.
A lwa ys re member that the airbag system can on ly help to protect
you if you a re wearing your safe ty belt and weari ng it properly . T hi s .,,_

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• in side collisions when the acceleration measured by the sensor
is too low
• in front -end collisions
• in rear -end collisions
• in rollovers.
In some types of accidents the front airbags, side curtain airbags
and side airbags may be triggered together.
& WARNING
• Safety belts and the airbag system will only provide protection
when occupants are in the proper seating position
~ page 240.
• If the airbag indicator light comes on when the vehicle is being
used , have the system inspected immediately by your authorized
Audi dealer . The airbag may not work properly when the vehicle
acceleration in a side collision is high enough to activate the
airbag .•
How supplemental side airbags work
Side airbags deploy instantly and can help reduce the risk
of upper torso injuries for occupants who are properly
restrained.
Fig. 239 Inflated side
airbags on left side of
vehicle, rear s ide
airbag
When the system is triggered, the airbag is filled with propellant gas
and breaks through a seam in the seat surface area marked
"AIRBAG" . It expands between the side trim panel and the
passenger. In order to he lp provide this additional protection, the
side airbag must inflate within a fraction of a second at very high
speed and with great force . The supplemental side airbag could
injure you if your seating position is not proper or upright or if items
are located in the area where the supplemental side airbag expands.
This applies especially to children~
page 245, "Child Safety".
Supplem ental side airbags inflate between the occupant and the
door panel on the side of the vehic le that is struck in certain side
collision~ fig. 239.
Although they are not a soft pillow, they can "cushion" the impact and in this way they can he lp to reduce the risk of injury to the upper
part of the body.
A fine dust may develop when the airbag deploys. This is normal
and does not mean there is a fire in the vehicle. •
Important safety instructions on the side
airbag system
Airbags are only supplemental restraints. Always prop­
erly wear safety belts and ride in a proper seating posi­
tion .
There is a lot that you and your passengers must know and act
accordingly to help the safety belts and airbags do their job to
provide supplementa l protection.
& WARNING
An inflating side airbag can cause serious or fatal injury. Improp ­
erly wearing safety belts and improper seating positions increase
the risk of serious personal injury and death whenever a vehicle is
being used . _.,

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& WARNING (continued)
• In order to reduce the risk of injury when the supplemental side
airbag inflates:
-Always sit in an upright position and never lean against the
area where the supplemental side airbag is located .
- Never let a child or anyone else rest their head against the
side trim panel in the area where the supplemental side airbag
inflates.
- Always make sure that safety belts are worn correctly,
- Do not let anyone sitting in the front seat put their hand or any other parts of their body out of the window.
• Always make sure that the side airbag can inflate without inter ­
ference.
-Never install seat covers or replacement upholstery over the
front seat backs that have not been specifically approved by
Audi.
- Never use additional seat cushions that cover the areas
where the side airbags deploy .
- Damage to the original seat covers or to the seam in the area
of the side airbag module must always be repaired immedi­
ately by an authorized Audi dealer .
• Objects between you and the airbag can increase the risk of
injury in an accident by interfering with the way the airbag unfolds
or by being pushed into you as the airbag inflates .
- Never place or attach accessories or other objects (such as
cup holders, telephone brackets, or even large, bulky objects)
on the doors, over or near the area marked "AIRBAG" on the
seat backrests .
- Such objects and accessories can become dangerous projec­
tiles and cause injury when the supplemental side airbag deploys.
Controls and equip­ ment Safety first
Vehicle operation
& WARNING (continued)
-Never carry any objects or pets in the deployment space
between them and the airbags or allow children or other
passengers to travel in this position .
• Always use the built -in coat hooks only for lightweight
clothing. Never leave any heavy or sharp-edged objects in the
pockets that may interfere with side airbag deployment and can
cause personal injury in an accident .
• Always prevent the side airbags from being damaged by heavy
objects knocking against or hitting the sides of the seatbacks.
• The airbag system can only be triggered once. If the airbag has
been triggered, the system must be replaced by an authorized
Audi dealership.
• Damage (cracks, deep scratches etc.I to the original seat covers
or to the seam in the area of the side airbag module must always
be repaired immediately by an authorized Audi dealer.
• If children are seated improperly, their risk of injury increases
in the case of an accident=>
page 245, "Child Safety".
• Never attempt to modify any components of the airbag system
in any way.
• In a side collision, side airbags will not function properly if
sensors cannot correctly measure increasing air pressure inside
the doors when air escapes through larger, unclosed openings in
the door panel.
-Never drive with interior door trim panels removed.
- Never drive when parts have been removed from the inside
door panel and the openings they leave have not been properly
closed.
- Never drive when loudspeakers in the doors have been
removed unless the speaker holes have been properly closed .
- Always make certain that openings are covered or filled if
additional speakers or other equipment is installed in the
inside door panels.
Vehicle care Do-it-yourself service Technical data

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& WARNING (c ont in ued)
- Alwa ys ha ve work on th e doo rs done by an auth ori ze d Aud i
d ea le r or q ualified works hop . •
Side curtain airbags
Description of side curtain airbags
The side curtain airbag system can provide supplemental
protection to pr operly restrained occupants .
Fig. 240 Side cu rtai n
ai rb ags, drive r's side:
s ide c urt a in airb ag
l oca tion
The side curtain airbags are located on both sides of the interior
above the front and rear side windows~ fig. 240. They are identi ­
fied by the word "AIRBAG" on the windshield frame and the center
roof pillar.
The side curtain airbag system supplements the safety belts and can help to reduce the risk of injury for occupants' heads and upper
torso on the side of the vehicle that is struck in a side collision. The
side curtain airbag inflates only in side impacts and on ly when the
vehic le acceleration registered by the control unit is high enough . If
t his rate is below the re ference value programmed into the control
unit, the side airbags will not be triggered, even though the car may
be badly damaged as a result of the collision . It is not possib le to
define an airbag triggering range that will cover every possible angle of
impact, since the circumstances will vary considerably
be tween one collision and another. Important factors include, for
example, the nature (hard or soft) of the impacting object, the ang le
of impact, vehicle speed, etc.~
page 243, "How side curtain airbags
work" .
Aside from their normal safety function, safety belts work to help
keep the dr iver or front passenger in position in the event of a colli ­
sion so that the side curtain airbags can prov ide protection .
The airbag system is not a substitute for your safety belt. Rathe r, it
is part of the overall occupant restraint system in your vehicle .
A lways remember that the airbag system can on ly help to protect
you if you are wearing your safety belt and wearing it properly. This
is another reason why you should always wear your safety belts, not
just because the law requires you to do so~
page 211, "General
notes".
It is important to remember that while the side curtain airbag
system is designed to he lp reduce the like lihood of serious injuries,
other injuries, for example, swelling, bruising, and minor abrasions
can a lso be associated with these airbags upon deployment.
Remember too, these airbags wi ll dep loy only once and only in
certain kinds of accidents -your safety belts are always there to
offer protection.
Th e s ide cu rtai n air ba g sys te m b asi ca lly co nsis ts of:
• The electronic control modu le and external side impact sensors
• T he side curtain airbags above the front and rear side windows
• The airbag indicator light in the instrument panel
The airbag system is monitored electronically to make certain it is
funct ion ing proper ly at all times . Each time you turn on the ignition,
the airbag system indicator light will come on for a few seconds (self diagnostics).
The s ide c urtain a irbag is no t activa te d:
• if the ignition is tu rned off,

• in side collisions when the acceleration measured by the sensor
is too low,
• in front -end collisions,
• in rear-end collisions,
• in rollovers.
& WARNING
• Safety belts and the airbag system will only provide protection
when occupants are in the proper seating position
=> page 86,
"General recommendations" .
• If the airbag indicator light comes on when the vehicle is being
used, have the system inspected immediately by your authorized
Audi dealer . The side curtain airbag may not work properly even
when the vehicle acceleration in a side collision is high enough to
activate the airbag.
c:J
How s ide curtain airbags work
Side curtain airbags can work together with side airbags
to help reduce the risk of head and upper torso injuries for
occupants who are properly restrained.
Safety first
Fig. 241 Illustration o f
prin ciple: Inflated side
c urtain airbags on the
left side
Airbag system
The side curtain airbags inflate between the occupant and the
windows on the side of the vehicle that is struck in a side collision
=> fig. 241 .
When the system is triggered, the side curtain airbag is filled with
propellant gas and breaks through a seam above the front and rear
side windows identified by the AIRBAG label. In order to help
provide this additional protection, the side curtain airbag must
inf late within the blink of an eye at very high speed and with great
f orce . The side curtain airbag could injure you if your seating posi­
tion is not proper or upright or if items are located in the area where
the supplementa l side curtain airbag inflates . This applies espe ­
cially to children=>
page 245.
Although they are not a soft pil low, side curtain airbags can
"cushion" the impact and in this way they can help to reduce the risk
of injury to the head and the upper part of the body.
A fine dust may develop when the airbag deploys. This is quite
normal and does not mean there is a fire in the vehic le .•
Important safety instructions on the side
curtain airbag system
Airbags are only supplemental restraints. Always prop­
erly wear safety belts and ride in a proper seating posi­
tion.
There is a lot that you and your passengers must know and do to
help the safety belts and airbags do the ir job to provide supple­
mental protection.
& WARNING
Improperly wearing safety belts and improper seating positions
increase the risk of serious personal injury and death whenever a
vehicle is being used. •
Vehicle care I I irechnical data

-Child Safety -------=---------------------------------------
& WAR NIN G (co ntinued )
• Alw ays in sta ll re ar-facin g child safety s eats on the r ear seat .
• If you m us t in sta ll a rear ward f acing child saf ety s eat on th e
fr ont pa ssenger seat in exceptional circum stan ces and the
PA SSEN GER AIR BAG OFF light do es not come on and sta y on ,
immediately in sta ll the re ar-facing child safety s eat in a rear
s eating po sit ion and ha ve th e airb ag s ystem insp ected immedi ­
atel y by your Audi dea ler .
& WARNING
If, in exceptional circum stance s, you mu st in sta ll a forward -f a cing
c hild re str ain t on th e fr ont p assenger's s eat:
• Always mak e sure the forward -fac ing seat ha s been de signed
a nd ce rt ified by it s m anufa cturer for u se on a fr ont se at w ith a
pa ssenger front and side airbag.
• Always follow the m anufacturer's instru ctions provided w ith
the child safety seat or carr ier.
• Alwa ys mo ve the pa ssenger seat into it s rea rmost positi on in
the seat' s fore and aft adju stment range , as far aw ay from the
ai rbag as possib le bef ore installing the ch ild r estr aint . The ba ck­
re st mu st b e adjusted to an upright po sition.
• Alway s m ake sure that the PASSENGER AIR BAG OFF l ight
c om es on and sta y s on all the time whenever the ignition is
s w it c hed on . •
Advanced front airbag system and children
Your vehicle is equipped with an "Advanced Airbag System" in
complia nce with United States Federa l Motor Vehicle Safety Stan ­
dard (FMVSS) 208 as applicable at the time your vehicle was manu ­
factu red. T
he Advanced Airbag system in your vehicle has been certified to
meet the " low -risk" requirements for 3 and 6 year -old chi ldren on
the passenger side and smal l adults on the driver side . The low risk
deployment criteria are intended to reduce the risk of injury through
interaction with the airbag that can occur, for example, by being too
close to the steering wheel and instrument panel when the airbag
inflates. In addition, the system has been certified to comply with
the "suppression" requirements of the Safety Standard, to turn off
the front airbag for infants up to 12 months who are restrained on
the front passenger seat in child restraints that are listed in the
S tandard.
Even though your vehicle is equipped with an Advanced Airbag
system, all ch ildren, especially those 12 years and younger, should
always ride in the back seat properly restrained for their age and
size . The airbag on the passenger side makes the front seat a poten­
tially dangerous p lace for a child to ride. The front seat is not the
safest p lace for a child in a forward -facing child safety seat. It can be
a very dangerous p lace for an infant or a larger ch ild in a rearward­
facing seat. •
Advanced Airbags and the weight-sensing
mat in the front seat
The Advanced Airbag System in your vehicle detects the presence
of an infant or child in a chi ld restraint on the front passenger seat
using the weight -sensing mat in the seat cushion and the sensor
below the safety belt latch on the front passenger seat that
measures the tension on the safety belt.
The weight -sensing mat measures total weight of the chi ld and the
child safety seat and a child blanket on the front passenger seat . The
weight on the front passenger seat is related to the design of the
child restraint and its "footprint", the size and shape of the bottom
of the child restraint as it sits on the seat . The weight of a child
restraint and its "footprint" vary for different kinds of child ..,.

-----------------------------------------~C::_! h~ i~ ld ~ S~a !_!f ~e _!;tY L _ffllll
restraints and for the different models of the same kind of child
restraint offered by child restraint manufacturers.
The weight ranges for the individual types, makes and models of
child restraints that the NHTSA has specified in the Safety Standard
together with the weight ranges of typ ical infants and typical 1 year­
old child have been stored in the control unit of the Advanced
Airbag System. When a child restraint is being used on the front
passenger seat with a typical 1 year -old child, the Advanced Airbag
System compares the weight measured by the weight sensing mat
with the information stored in the electronic control unit.
The electronic control unit also registers the tension on the front
passenger safety belt. The tension on the safety belt for the front
passenger seat will be different for an adult who is properly using
the safety belt as compared to the tension on the belt when it is
used to attach a child restraint to the seat. The sensor below the
latch for the safety belt for the front seat passenger measures the
tension on the belt . The input from this sensor is then used with the
weight to "decide" , whether there is a child restraint with a typical 1
year-old child on the front passenger seat and whether or not the airbag must be turned off.•
Child restraints and Advanced Airbags
Regardless of the child restraint that you use, make sure that it has
been certified to meet United States Federal Motor Vehicle Safety
Standards and has been certified by its manufacturer for use with
an airbag. Always be sure that the chi ld restraint is properly
installed at one of the rear seating positions. If in exceptiona l
circumstances you must use it on the front passenger seat, carefully
read all of the information on child safety and Advanced Airbags
and heed a ll of the applicable WARNINGS. Make certain that the
child restraint is correctly recognized by the weight -sensing mat
inside the front passenger seat, that the front passenger airbag is
turned off and that the airbag status is always correctly signaled by
th e
PASSENGER AIR BAG OFF light .
Controls and equip­
ment Safety first Vehicle operation
Many
types and models of child restraints have been available over
the years, new mode ls are introduced regularly incorporating new
and improved designs and older mode ls are taken out of produc­
tion. Child restraints are not standardized . Child restraints of the
same type typically have different weights and sizes and different
'footprints,' the size and shape of the bottom of the chi ld restraint
that sits on the seat, when they are installed on a vehicle sea t. These
differences make it virtual ly impossible to certify comp liance with
the requirements for advanced airbags with each and every child
restraint that has ever been sold in the past or will be sold over the
course of the usefu l life of your vehic le.
For this reason, the United States National Highway Traffic Safety
Administration has pub lished a list of specific type, makes and
models of child restraints that must be used to certify compliance
of the Advanced Airbag System in your vehicle with the suppression
requirements of Federal Motor Vehicle Safety Standard 208. These
child restraints are:
A. Car beds, manufactured on or after September 1,
2004:
• Cosco Dream Ride 02-719
B. Rear facing child restraint systems, manufactured
on or after September 1, 2004:
(When the restraint system comes equipped with a removable base,
compliance has to be certified with or without the base) .
• Britax Handle with Care 191
• Century Assura 4553
• Century Smart Fit 4543
• Cosco Arriva 02727
• Evenflo Discovery Adjust Right 212
• Evenflo First Choice 204
• Graco lnfant8457
Vehicle care Do-it-yourself service Technical data

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Intelligent technology
Notice about data recorded by
vehicle control modu les
Your vehicle is not equipped with an Event Data Recorder (EDR),
installed by some manufacturers for the express purpose of
capturing data for retrieval after an accident or crash event . EDR's
are sometimes called "crash recorders" .
Some state laws restrict the retrieva l or downloading of data stored
by EDR's that were insta lled in a vehicle for the express purpose of
retrieving data after an accident or crash event without the owner's
consent.
Although your vehicle is not equipped with an EDR, it is equipped
with a number of electronic control modules for various vehicle systems such as, for example, engine function, emission control, as
well as for the airbags and safety belts.
These electronic control modules also record vehicle-related data during norma l vehicle operation for diagnost ic and repair purposes .
The recording capacity of the electronic control modules is limited
to data (no sound is recorded) and only a small amount of data is
actually recorded over a very limited period of time and stored when
a system fault or other condition is sensed by a control unit. Some
of the data then stored may relate to vehicle speed, direction, braking as well as restraint system use and performance in the
event of a crash or other condition . Stored data can only be read and
down loaded with special equipment .•
Electron ic Stabilizat ion Program (ESP)
General =nformation
The ESP improves the vehicle stability.
I~
"' " "'
- -
( ra I 5£ IA I -3, )
Fi g. 256 C ente r
co nso le w it h ES P
swi tch
ESP is designed to he lp you maintain vehic le control in situations
where the car approaches the limits of "grip", especia lly when
accelerating and cornering. ESP reduces the risk of skidding and
improves stabil ity under all road conditions .
T he system operates across the entire speed range in combination
with the ABS system. If the Anti-Lock Brake System (ABS) malfunc­
tions, the ESP wil l also shut down .
How th e sys te m w ork s
The Anti -Lock Brake System (ABS) , Electronic Differential Lock (EDU
and the Anti-Slip Regulation System (ASR) are integrated in the e lec­
tronic stabi lization program . In addition to the data provided by
these functions, the ESP control unit requires additional measure­ ment data provided by high performance sensors . The rotational
speed of the vehic le about its vertical axis, the lateral acce leration
acting on the vehicle, the brake pressure and the steering angle are
a ll measured .

The direction in which the driver wishes to travel is determined with
t he aid of the steering angle and vehicle speed and is continua lly
compared with the actual behavior of the vehicle. If the two do not
match, for example, when the vehic le starts hydrop laning on a wet
road, ESP will automatically brake the appropriate whee l to correct
the prob lem.
The vehicle is then stab ilized by the forces acting on the whee l
during braking. If the vehicle is oversteering (rear tends to skid out
of the turn), the brakes are mainly app lied on the wheel that is on
the outside of the curve. In the case of a vehicle that is understeering
(tendency to sl ide out of the curve), the brakes are applied at the
rear wheel that is on the inside of the curve . An acoustic signal indi­
cates when ESP brake application cuts in
~ & .
The system operates across the entire speed range in combination
with the ABS system
~ page 274 . If the Anti -Lock Brake System
(ABS) malfunctions, the ESP wi ll be out of action as well.
Ac tivat ion
When you turn on the eng ine, ESP will automatically be activated
and will perform a self -test.
The system can be activated or deactiva ted by pressing the button
~ page 270, fig. 256. The warning light comes on when the system
is switched off
~ page 18.
Normally , the ESP should always be on, however, it may be advanta­
geous to turn off the system in certain special cases when some
degree of wheel spin is desired such as :
• when driving with snow chains
• when driving in deep snow or on a loose surface (to allow the
wheels to dig in to reach firm ground)
• when trying to "rock" the vehicle free when it has beco me stuck.
T he system should be reactivated once you are no longer in such
situations .
Both the ABS and EDS systems are still functioning even if the ESP
is switched off .
Controls and equip­
ment Safety first Vehicle operation
In
te llig ent tec hn olo gy
& WARNING
The Ele ctron ic St abiliz ation Progr am i s ne ve rt h el ess s ubject to the
laws of ph ysics. It i s particularl y important t o pay attention t o th is
f ac t on wet an d slipp ery road s. It i s th ere fore important that you
alway s adapt your driving to the condition of the road and traffic
c onditio ns. Do n ot allow the in crease d sa fety p ro vi ded by t he El ec­
tronic Stabiliz ation Program sy stem to lu ll you into a ccepting
a dditional safety ri sk s.
c
Electronic differential lock (EDL)
The electronic differential lock monitors the rotation al
s p eed of the drive wheels.
G en era l not es
The elect ronic differential lock (EDU helps the car to start moving,
accelerate and c limb a gradient on surfaces providing poor or
a lmost no grip . Without EDL , this would be difficult, if not impos ­
s ib le.
How the system works
The EDL operates automatical ly. It monitors the rotational speed of
the drive wheels on an axle with the he lp of the ABS sensors
~ page 274. If a noticeable difference in rotational speed between
the drive wheels on one axle is detected (e.g. on slippery ground on
one side), the spinning w heel is braked, thereby transferring power
to the other drive wheel or wheels (all -whee l drivel. This is done up
to a speed of about 60 mph (100 km/h) . Noises from the brake
system signal that wheel spin is being control led .
Dri ving off
When driving off, always be sur e to ke ep road conditions in mind as
you accelerate. I f one drive wheel spins because it is on a surface
with less grip, gradual ly increase the pressure on the accelera tor
pedal unt il the car star ts to
move . The whee l less able to t ra nsfer
power spins. _.,
Vehicle care Do-it-yourself service Technical data