sensor AUDI S4 CABRIOLET 2009 Owner's Manual

___ A_ ir_ b_ a~g _ s_ y_ s_ t _e_ m ___________________________________________________ _
passenger seat shou ld be turned off o r not=> page 1 70, "C hild
r es train ts on the fron t sea t - som e impo rtant thin gs to kno w".
• A sensor in the safety belt latch for the driver and fo r the front
s e at pass enger that s enses w hether tha t sa fety b elt is la tc he d o r no t
and transmits this information to the el ectronic control unit.
& WARNING
Damage to the front passenger seat can prevent the front airbag
from working properly .
• Improper repair or disassembly of the front passenger and
driver seat will prevent the Advanced Airbag System from func ­
tioning properly.
• Repairs to the front passenger seat must be performed by qual­
ified and properly trained workshop personnel.
• Never remove the front passenger or driver seat from the
vehicle.
• Never remove the upholstery from the front passenger seat .
• Never disassemble or remove parts from the seat or disconnect
wires from it .
• Never carry sharp object s in your pockets or place them on the
seat . If the weight-sensing mat in the passenger seat is punctured
it cannot work properly.
• Never carry things on your lap or carry objects on the
passenger seat. Such items can increase the weight registered by
the weight-sens ing mat and send the wrong information to the
airbag control unit .
• Never store items under the front passenger seat. Parts of the
Advanced Airbag System under the passenger seat could be damaged , preventing them and the airbag system from working
properly.
• Never place seat covers or replacement upholstery that have
not been specifically approved by Audi on the front seats.
& WARNING (continued )
• Seat covers can prevent the Advanced Airbag System from
recognizing child restraints or occupants on the front passenger
seat and prevent the side airbag in the seat backrest from
deploying properly .
• Never use cushions, pillows, blankets or similar items on the
front passenger seat . The additional padding will prevent the
weight-sensing mat in the seat from accurately registering the
child restraint or person on the seat and prevent the Advanced
Airbag System from functioning properly.
• If you must use a child restraint on the front passenger seat
and the child restraint manufacturer's instructions require the use
of a towel , foam cushion or something else to properly position
the child restraint , make certain that the PASSENGER AIR BAG OFF
light comes on and stays on whenever the child restraint is
i nstalled on the front passenger seat .
• If the PASSENGER AIR BAG OFF light does not come on and stay
on , immediately install child restraint in a rear seating position
and have the airbag system inspected by your Audi dealer. •
How the Advanced Airbag System
components work together
The front Advanced Airbag System and the si de airba gs supp lement
t h e protection offe red by the front three -point safety be lt s with
pretensioners and load limiters and the adjustab le head restraints
to help reduce the risk of in jury in a wide range of accident and
cras h situati ons . Be sure to read the im por tant in fo rmati on a bout
safety and heed the WARN INGS in this chapter.
De ploy men t of the Advanc ed A ir b ag Syst em and the activa tion of
th e safety belt pretens ioner d epends on the dece leration measured
b y the c ra sh se nsors and reg istered by the elec tronic co ntrol un it .
C rash severity depends on speed and dece leration as well as the
mass an d stiff ness of the vehicle o r obj ect invo lved in the c ra sh.
~

__________________________________________________ A_ i_ r _b _a...; g::- s_ y=--- s_t _e _m ___ __
& WARNING (continued )
airbag dur ing braking or in a sudden maneuver . Objects ne ar the
airbags can become proje ctiles and cau se injury , particularly when
the seat is reclined .
• Never tilt the front passenger seat backrest forward when the
vehicle is moving . An inflating airbag will force the backrest back­
ward and can injure rear seat occupants.
_& WARNING
The fine dust created when airbags deploy can cause breathing problems for people with a history of asthma or other breathing
conditions.
• To reduce the risk of breathing problems, those with asthma or
other respiratory conditions should get fresh air right away by
getting out of the vehicle or opening windows or doors.
• If you are in a collis ion in which airbags deploy, wash your
hands and face with mild soap and water before eating.
• Be careful not to get the dust into your eyes , or into any cuts or
scratches .
• If the residue should get into your eyes, flush them w ith
water. •
Monitoring the Advanced Airbag
System
Airbag monitoring indicator light :~
Two sep arate in dica tors m onitor the fu ncti on of th e
Adv anced A irba g Sys tem: the airbag moni tor ing in dica to r
l ight and t he
PASSENGER AIR BAG OFF light.
The Advanc ed A ir b ag S yst em (includ ing the e lec tronic co ntro l unit,
sensor c ircuits and system wiring) is monitored continuously to
Controls and equip­ ment Safety first Vehicle operation make sure that it is functioning properly whenever the ignition is on
.
Eac h tim e you tu rn on t he ignit io n, th e airbag monitoring ind ica tor
light
fl wi ll come on for a few seconds (self diagnostics) .
The system must be inspected when the indicator l ight ~:
• do es not com e on when the ig nit ion is sw itch ed on,
• does not go out a few seconds after you have switched on the
i gni tion , or
• comes on while driving.
I f an a irbag s ystem malfu ncti on is detec ted , the indi cator light will
first start flash ing to catch the driver's attention and then sta y on
co nti nuou sly to serve as a constant r eminder to h ave the sys tem
inspected immediately.
If a malf unctio n occurs that t urns the front airbag on the passenger
s id e off , the PASS ENGER AIR BAG OFF light w ill come on a nd s ta y on
whenever the ig nition is on.
_& WARNING
An airbag system that is not functioning properly cannot provide
s upplemental protect ion in a frontal crash .
• If the airbag indicator light comes on , it means that there may
be something wrong with the Advanced Airbag System . It is
possible that the airbag will inflate when it is not supposed to, or
will not inflate when it should .
• Have the airbag system inspected immediately by your Audi
dealer. •
Vehicle care Do-it-yourself service Technical data

___ A_ ir_b_ a..::g =-- s__,y:.... s_ t _e_ m ___________________________________________________ _
PASSENGER AIR BAG OFF light
............. Fig. 174 Section from
the instrument panel:
PASSENGER AIR BAG
OFF light
The PASSENGER AIR BAG OFF light is located in the center of the
instrument panel
~ fig. 174.
The
PASSENGER AIR BAG OFF light will come on and stay on to tell
you when the front Advanced Airbag on the passenger side has
been turned off by the electronic control unit . Each time you turn on
the ignition , the
PASSENGER AIR BAG OFF light will flash for a few
seconds and :
• will stay on if the front passenger seat is not occupied,
• will stay on if there is a small child or child restraint on the front
passenger seat,
• will go out if the front passenger seat is occupied by an adult as
registered by the weight -sensing mat .
The
PASSENGER AIR BAG OFF light must come on and stay on if the
ignition is on and
• a car bed has been installed on the front seat, or
• a rearward-facing child restraint has been installed on the front
passenger seat, or
• a forward-facing child restraint has been installed on the front
passenger seat, or
• the weight registered on the front passenger seat is equal to or
less than the combined weight of a typical 1 year-old restrained in one of the rear-facing or forward-facing infant restraints
listed in
Federal Motor Vehicle Safety Standard 208 with which the Advanced
Airbag System in your vehicle was certified .
If the front passenger seat is not occupied, the front airbag will not
deploy, and the
PASSENGER AIR BAG OFF light will stay on. Never
install a rearward -facing child restraint on the front passenger seat,
the safest place for a child in any kind of child restraint is at one of
the seating positions on the rear seat~
page 170, "Child restraints
on the front seat- some important things to know" and~
page 190,
"Child Safety".
If the PASSENGER AIR BAG OFF light comes on when one of the
conditions listed above is met, be sure to check the light regularly
to make certain that the
PASSENGER AIR BAG OFF light stays on
continuously whenever the ignition is on. If the
PASSENGER AIR
BAG OFF
light does not appear and not stay on all the time, stop as
soon as it is safe to do so and
• reactivate the system by turning the ignition off and then turning
it on again;
• remove and reinstall the child restraint. Make sure that the child
restraint is properly installed and that the safety belt for the front
passenger seat has been correctly routed around the child restraint
as described in the child restraint manufacturer's instructions;
• make sure that the convertible locking feature on the safety belt
for the front passenger seat has been activated and that the safety
belt has been pulled tight . The belt must not be loose or have loops
of slack so that the sensor below the safety belt latch on the seat can
do its job
~ page 200.
• make sure that things that may increase the weight of the child
and child safety seat are not being transported on the front
passenger seat;
• make sure that the safety belt tension sensor is not blocked.
Shake the safety belt latch on the front passenger seat back and
forth;
• If a strap or tether is being used to tie the child safety seat to the
front passenger seat, make sure that it is not so tight that it causes _,,

__________________________________________________ A_ i_ r _b _a...; g::- s_ y=--- s_t _e _m ___ lffllll
& WARNING (continued )
• Always make sure that the side airbag can inflate without inter­
ference :
- Never install seat covers or replacement upholstery over the
front seatbacks that have not been specifically approved by
Audi.
- Never use additional seat cushions that cover the areas
where the side airbags inflate.
- 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.
• The airbag system can be activated only once. After an airbag
has inflated, it must be replaced by an authorized Audi dealer or
qualified technician who has the technical information , training
and special equipment nece ssary.
• The airbag system can be deployed only once . After an airbag
has been deployed , it must be replaced with new replacement
part s designed and approved especially for your Audi model
version. Replacement of complete a irbag systems or airbag
components must be performed by qualified workshops only .
Make sure that any airbag service action is entered in your Audi
Warranty
& Maintenance booklet under AIRBAG REPLACEMENT
RECORD .
• In accidents when an airbag is deployed , the vehicle battery
s eparates the alternator and the starter from the vehicle electrical
system for safety reasons with a pyrotechnic circuit interrupter.
-Work on the pyrotechnic circuit interrupter must only be
performed by a qualified dealer -risk of an accident !
- If the vehi cle or the circuit interrupter is scrapped , all appli ­
cable safety precautions must be followed . •
Controls and equip­ ment Safety first
Vehicle operation
Other things that can affect Advanced Airbag
performance
Changing the vehicle 's suspension system can cha nge the way that
the Advanc ed Ai rbag Syste m perfor ms in a cras h. Fo r ex amp le,
u sing tire -rim combinations not a pproved by Audi, lowering the
ve hicle , c hang ing the st iffness o f the suspe nsion, inclu din g the
spr ings, s uspension struts, shock absorbers etc. can change the
fo rc es that ar e meas ured by th e a irbag sens ors and sent to the e lec ­
tronic control un it. Some suspens ion changes can, for example,
in crea se th e fo rc e leve ls meas ured by th e se nsors and ma ke t he
airbag system dep loy in crash es in wh ich it wou ld not dep loy if the
c h anges had no t been m ade . Ot her k in ds of cha nge s m ay red uce
the fo rce levels measured by the sensors and p revent t he airba g
fr om depl oyin g whe n it should.
T he sensors in the safe ty b elt b uckle fo r the driver a nd front
passenger seat te ll the electronic control module if the safety belt is
l a tc h e d or not. If the s afe ty be lt is bei ng use d, t he fr ont ai rbag w ill
dep loy at a s lightly higher rate of vehic le dece leration than if the
sa fe ty belt is not be ing used . T here for e, in a partic ular co lli sion , it is
possible t hat an airbag will not dep loy at a seating position w here
the safe ty belt is b ein g us ed b ut will infl ate a t th e po siti on w here the
safety belt is not being used. It is important that nothi ng interfere
with the safety belt b uck les so that the sensors can send the correct
i nformat ion about safety b elt use to the electronic control un it.
& WARNING
Changing the vehicle's suspension including use of unapproved
tire -rim combinations can change Advanced Airbag performance
and increase the risk of serious personal injury in a crash.
• Never install suspension components that do not have the
same performance characteristics as the components originally
installed on your vehicle .
• Never use tire-r im combinations that have not been approved
by Audi. .,.
Vehicle care Do-it-yourself service Technical data

Side airbags
Description of side airbags
The airbag system can provide supplemental protecti on
to pro perly restrained fr ont seat occupants.
Fi g. 177 Si de air bag
l oca tio n in th e driv er's
sea t
The s ide airbags are located in the sides of the front seat backrests
=> fig. 177 facing the doors. They are identified by the word
" AIRBAG" .
The side airba g sy stem b asica lly con sis ts of :
• the electronic contro l module and external side impact sensors
• the two s ide airbags located in th e sides of the front backrests
• the airbag warning light in the instrument cluster .
Th e airbag system is monitored elec tronically to make certain that
it is function ing properly at all times . Each time you turn on the igni ­
tion , the airbag system indicator light will come on for a few
seconds (self diagnostics).
The side airbag system supplements the safety belts and can help to reduce the risk of injury to the driver 's and front passenger 's
uppe r torso on the side of the vehicle that is struck in a side co lli­
sion . The airbag d eploys only in side impacts and on ly when the
vehicle acceleration registered by the contro l unit is high enough. If
this rate is below the reference value programmed into the contro l
Safety first
Airbag syst em
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 possible to
def ine an airbag trigger ing range that will cover every possible
ang le of impact, since the circumstances will vary considerably
between one collision and another . Important factors include , for
examp le, the nature (hard or soft) of the impacting object, the angle
of impact, vehicle speed, etc.=>
page 188, "Impo rtant safety
instructions on the side airbag system" .
Aside from their norma l safety function, safe ty bel ts work to help
keep the driver or front passenger in position in the event of a side
coll ision so that the side airbags can provide protec tion .
The airbag system is
not a subst itute for your safety belt . Rather , it
is part of the overall occupant restraint system in your vehicle.
Always remember that the side airbag system can on ly he lp to
protect you if you are wearing your safety belt and wearing it prop ­
erly. This is another reason why you should a lways wear your safety
belts, not just because th e law requires you to do so~
page 159 ,
"Genera l notes".
It is important to remember that while the supp lementa l side airbag
system is designed to reduce the likelihood of serious injuries, othe r
injuries , for example, swelling , bruising, and minor abras ions can
also be associated with deployed side airbags . Remember too, side
airbags will deploy only once and on ly in certain kinds of accidents
- your safety belts are a lways there to off er protection.
Vehic le damage , repair costs or even the lack of veh icle da mage are
not necessarily an indica tion of over -sensitive or failed airbag acti­
va tion. In some collision s, both front and side airbags may infla te .
Remember too, that airbags will deploy on ly once and only in
certain kinds of collisions -your safety belts are always there to
offer protection in those acc idents in which airbags are not
suppos ed to deploy or when they hav e already deployed .
The si de airbag system will not d eploy :
• when the ig nition is turned off
• in side collisions when the acceleration measured by the sensor
is too l ow ..
~ehicle care Technical data

__________________________________________________ A_ i_ r _b _a...; g::- s_ y=--- s_t _e _m ___ lllll
& WARNING (continued)
-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.
- 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 .
Controls and equip­ ment Safety first
Vehicle operation
& WARNING (continued)
• 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 190, "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 .
- Always have work on the doors done by an authorized Audi
dealer or qualified workshop . •
Vehicle care Do-it-yourself service Technical data

--------------------------------------------~C~ h~ il~d ~S~ a~f e~ t~ YL _III
& WA RNIN G (conti nu ed )
• Alway s install rear-facing child safety se ats on the rear seat.
• If you mu st in stall a rearw ard f acing chi ld safety seat on the
front pa ssenger seat in exc eptional cir cum stance s and the
PA SSENGER AIR BAG OFF light do es not come on and stay on,
im medi ate ly install the re ar-fa cing child safety s eat in a rear
s e ating po sit ion and h ave the airb ag sys tem inspe cted im medi ­
ately by your Audi de aler .
& WARNING
If, in exceptional circum stance s, you must in stall a forward -facing
c hild re st ra int on the fr ont p ass eng er' s s eat :
• Alway s make sure the forward -facing seat ha s been de signed
and cert ified by it s manufa cturer f or use on a front se at with a
p ass enger front and side airbag .
• Always follow the m anufacturer's instruct ions provided with
the child safety seat or carrier.
• Alway s m ove the pa ss e nger sea t into its rearm ost p osit ion in
the seat' s fo re and aft adju stment r ange , as far away from the
a irb ag as possib le before installing the child r estr aint . The b ack­
rest mu st be adju sted to an upr ight po sition.
• Alw ays ma ke sure th at the PAS SENGER AIR BAG OFF light
c ome s on and stay s on all the time whenever the ignition i s
s witched on . •
Advanced front airbag system and children
Your vehicle is equipped with an "Advanced Airbag System" in
compliance with United States Federal Motor Vehicle Sa fety Stan ­
dard (FMVSS) 208 as applicab le at the time your vehicle was manu ­
factured .
Controls and equip­
ment Safety first Vehicle operation
The Advanced Airbag system in your vehicle has been certified to
meet the " low -risk" requirements for 3 and 6 yea r- old child ren on
the passenger side and small adu lts on the driver side. The low risk
deployment c rite ria are intended to reduce the risk of injury th rough
interaction with the airbag that can occur, for example, by being too
close to the steering whee l and instrument panel when the airbag
in flates . In add ition, the system has been cert ified 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
Standard.
Even though your vehic le is equipped with an Advanced Airbag
system, all ch ildren, especially those 12 years and younger, should
a lways ride in the back seat proper ly restrained for the ir age and
s ize . The a irbag on the passenger side makes the front seat a poten­
tially dangerous p lace for a chi ld to r ide. The front seat is not the
safest place for a chi ld in a forward -facing child safety seat. It can be
a very dangerous place for an infant or a larger chi ld 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 p resence
of an infant or chi ld 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 t otal weight of the ch ild and the
child safety seat and a chi ld blanket on the front passenger seat. The
weight on the front passenge r 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 .,
Vehicle care Do-it-yourself service Technical data

-Child Safety ____ .:....__ __________________________ _
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 typical 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 child restraint is properly
installed at one of the rear seating positions. If in exceptional
circumstances you must use it on the front passenger seat, carefully read all of the information on child safety and Advanced Airbags
and heed all 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
the
PASSENGER AIR BAG OFF light. Many types and models of child restraints have been available over
the years, new models are introduced regularly incorporating new
and improved designs and older models 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 child restraint
that sits on the seat, when they are installed on a vehicle seat. These
differences make it virtually impossible to certify compliance 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 useful life of your vehicle.
For this reason, the United States National Highway Traffic Safety
Administration has published 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 basel.
• 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 Infant 8457

-In
te llig ent tec hnolo gy --=---=-=-------------
Intelligent technology
Notice about data recorded by
vehicle control modules
Your vehicle is not equipped with an Event Data Recorder (EDRl,
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 examp le, engine function, emission control, as
we ll as for the airbags and safety belts.
T hese electronic control modules also record vehic le-rela ted da ta
during norma l ve hicle 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 vehic le speed, d irection,
braking as we ll 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. •
Electronic Stabilization Program (ESP)
General information
The ESP improves the vehicle s tability.
I
A F ig . 19 0 Cen ter
co nsol e w ith ESP
sw itch
ESP is designed to he lp you maintain vehic le control in situa tions
where the car approaches the limits of "grip", especially when acce lerating and cornering . ESP reduces the risk of skidding and
improves stability under all road conditions .
The syst em opera tes across the en tire speed range in combination
with the ABS system. If the Anti-Lock Brake System (ABS) malfunc ­
tions, the ESP wil l a lso shut down .
How th e sys te m work s
The Anti-Lock Brake System (ABS) , E lectronic Differential Lock (EDU
and the Anti -Sl ip Regu lation System (ASR) are integrated in the e lec­
tronic stabi li z ation program. In addition to the data provided by
these functions, the ESP control unit requires additional measure­ ment data provided by high performance sensors . T he rotational
speed of the vehic le about its ver tica l axis, t he late ral acce leration
acting on the vehic le, the brake pressure and the steering ang le are
a ll measured .

The direction in which the driver wishes to travel is determined with
the 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 vehicle starts hydrop laning on a
wet road -, ESP will automatical ly brake the appropriate wheel to
correct the problem.
The veh icle is then stabi lized by the forces act ing 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 whee l that is on
the outside of the curve. In the case of a vehicle that is understeering
(tendency to s lide 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 combinat ion
with the ABS system => page 216 . If the Anti -Lock Brake System
(ABS) malfunctions, the ESP wi ll be out of act ion as well.
Activa tion
When you turn on the engine, ESP w ill automatica lly be activated
and will perform a self -test .
The system can be activated o r deactivated by pressing the butto n
=> page 212, fig . 190 . The warning light comes on when the system
is switched off .
Normally, the ESP should a lways be on, however, it may be advanta­
geous to turn off the system in certain specia l cases when some
degree o f wheel spin is desired such as :
• when driving with snow chains
• when driving in deep snow or on a loose surface (to allow the
whee ls to dig in to reach firm ground)
• when trying to "rock" the vehicle free whe n it has become stuck .
The system shou ld be reactivated once you are no longer in such
situations.
Both , the ABS and EDL systems are still functioning even if the ESP
is switched off .
Controls and equip­
ment Safety first Vehicle operation
Int
ellig ent tec hnol ogy
& WARNING
The Ele ctron ic Stab ilization Program is neve rth ele ss s ubje ct to th e
law s of phy sic s. It is p art icularly important to pay at tent ion to thi s
f ac t on wet and slipper y ro ad s. It i s therefore important th at yo u
alway s adapt your driving to the condition of the road and traffic
c onditio ns. Do not allo w the in crea sed safety prov ided by t he Ele c­
tronic Stabilization Program sy stem to lull you into a ccepting
addition al safety ri sk s.
• Plea se note that when ESP i s deactivated , the drive wheel s can
s pin on icy and slippery ro ads a nd the vehi cle can break away -
d anger of skidding ! C
E lectronic differential lock CEDL)
The electronic differential lock monitors the rotational
speed of the drive wheels.
Gener al notes
The electronic differential lock (EDU helps the car to start moving,
accelerate and c limb a gradien t on surfaces providing poor or
a lmost no grip . Without EDL, this would be difficult , if not impos ­
sible.
How the syst em works
The EDL operates automat ical ly . It monito rs the rotationa l speed of
the drive whee ls on an axle with the he lp of the ABS sensors
=> page 216 . If a noticeable difference in rotational speed between
the drive wheels on one axle is de tected (e.g. on slippery grou nd on
one side), the spinning wheel is braked, thereby transferring power
to the other drive wheel or wheels (a ll -whee l drive) . 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.
~
Vehicle care Do-it-yourself service Technical data