
186Driving
If you select a gear which is lower than the gear shown on the instrument
panel display ⇒ Fig. 150, the gearbox will only shift down when there is no
longer a risk of over-revving the engine.
When the vehicle slows down (for instance when braking), the gearbox au-
tomatically shifts down into the next gear when the minimum engine speed
is reached.
Changing down to a lower gear increases the engine braking effect on
downhill gradients.
When the accelerator pedal is pressed right down past the point of resist-
ance at full throttle, the gearbox will select a lower gear ratio, depending on
road speed and engine speed.
Back-up programme
A back-up system is in place if a fault should occur in the
control system.
The automatic gearbox switches to the back-up programme if a fault should
occur in the control system. This is indicated by a gear pinion symbol which
lights up on the instrument panel display.
It is still possible to move the selector lever to all positions. The manual
shift programme (tiptronic) is not available when the back-up programme is
active.
Vehicles with tiptronic gearbox: When the selector lever is in position D or S
or in the manual shift programme, the gearbox will remain in 3rd gear if 1st,
2nd or 3rd gears were engaged when the fault occurred. The gearbox will
remain in 5th gear if 4th, 5th or 6th gears were engaged. The gearbox will
then engage 3rd gear when you drive away from a standstill or after the en-
gine is restarted. It will still be possible to use reverse gear in the normal way. However, the
electronic lock for reverse gear will be switched off.
CAUTION
Should the gearbox ever switch into the back-up programme, you should
take the vehicle to a technical service or specialised workshop as soon as
possible.
Steering wheel with paddle levers
The paddle levers on the steering wheel enable the driver to
manually select pre-programmed ratios or gears.
Fig. 151 Steering wheel:
tiptronic controls
– Briefly pull the left-hand paddle lever –
to change down to a
lower gear.
– Briefly pull the right-hand paddle lever +
to change up to a
higher gear.

188Intelligent technology
Practical Tips
Intelligent technology
Electronic Stability Control (ESC)
General Observations
The Electronic Stability Control increases the vehicle's stabil-
ity on the road.
Fig. 152 Centre console
with ESC switch
The ESC is designed to increase the degree of control in situations where
the vehicle approaches the limits of adhesion, especially when accelerating
and cornering. It reduces the risk of skidding and improves stability in all
road conditions. The system is active across the entire speed range. The anti-lock brake system (ABS), the electronic differential lock (EDL) and
the traction control system (ASR) are all integrated into the Electronic Stabil-
ity Control.
How it works
The ESC control unit processes data from the three integrated systems. It al-
so processes additional inputs provided by other high-precision sensors.
These register the vehicle's rotation about the vertical axis (yaw rate), later-
al acceleration, brake pressure and steering wheel angle.
The system uses the steering wheel angle and road speed to calculate the
changes of direction desired by the driver, and constantly compares them
with the actual behaviour of the vehicle. If the desired course is not being
maintained (for instance, if the vehicle is starting to skid), then the ESC
compensates automatically by braking the appropriate wheel.
The forces acting on the braked wheel bring the vehicle back to a stable
condition. If the vehicle
over swerves (tendency of the rear to leave the
road), the brakes will act on the front wheel facing the outside of the bend.
If the vehicle under swerves (tendency to leave the bend), the braking force
is applied to the rear wheel facing the inside of the bend.
The ESC works in conjunction with the ABS ⇒ page 189. If a malfunction
should occur in the ABS, the ESC will also stop working.
Deactivating
The ESC is activated automatically when the engine is started and performs
a self-test routine.
The ESC cannot be deactivated.

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WARNING
The ESC is not able to overcome the physical limits of adhesion. Even
with ESC, you should always adjust your speed to suit the road and traffic
conditions. Please bear this in mind, especially on wet or slippery road
surfaces. Do not let the extra safety features tempt you into taking any
risks when driving. Failure to do so could result in an accident.
Anti-lock brake system (ABS)
ABS prevents the wheels from locking up under braking.
The anti-lock brake system (ABS) is an important part of the vehicle's active
safety system. However, the ABS will not necessarily guarantee shorter
stopping distances in all conditions. For instance, on loose gravel or fresh
snow on top of an icy surface (conditions which anyway require extreme
care and reduced speed), the stopping distance with ABS may even be
slightly longer.
How the ABS works
The system runs an automatic self-check when the vehicle reaches a road
speed of about 6 km/h. This may be accompanied by a noise from the ABS
pump.
When one of the wheels is turning very slowly in relation to the road speed
and is close to locking up, the system will reduce the brake pressure on that
wheel. The driver is made aware of this adjustment process by a vibration of
the brake pedal and an audible noise. This is a deliberate warning to the
driver that one or more of the wheels is tending to lock up and the ABS con-
trol function has intervened. In this situation it is important to keep the
brake pedal fully depressed so the ABS can regulate the brake application,
but do not “pump” the brake pedal.
WARNING
The grip provided by ABS is still subject to the physical limits of adhe-
sion. Always bear this in mind, especially on wet or slippery roads. If you
notice that the ABS is working (to counteract locked wheels under brak-
ing), you should reduce speed immediately to suit the road and traffic
conditions. Do not let the extra safety features tempt you into taking any
risks when driving. Failure to do so could result in an accident.
Note
If a malfunction should occur in the ABS, this is indicated by a warning lamp
⇒ page 68.
Brake assist system
The brake assist system helps the driver to achieve optimum
braking effect.
The brake assist system helps to increase braking power and thus to ach-
ieve a shorter stopping distance. If the driver presses the brake pedal very
quickly, the brake assist system automatically boosts the braking force to
the maximum level, up to the point where the anti-lock brake function (ABS)
intervenes to stop the wheels from locking. You should then keep the brake
pedal pressed until the vehicle has braked to the required speed. The brake
assist system switches itself off as soon as you release the brake pedal.
The brake assist system will not be operative if there is a malfunction in the
ABS or the ESC.
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190Intelligent technology
WARNING
Please remember that the accident risk always increases if you drive too
fast, especially in corners or on a slippery road, or if you follow too close
behind the vehicle in front of you. An increased accident risk cannot be
compensated even by the brake assist system. Risk of accident.
Electronic differential lock (EDL)
The electronic differential lock prevents the loss of traction
caused if one wheel starts spinning. General notes
The electronic differential lock (EDL) helps the vehicle to start moving, ac-
celerate and climb a gradient in slippery conditions where this may other-
wise be difficult or even impossible.
How it works
The EDL works automatically, without the driver's involvement. With the aid
of the ABS sensors, the system monitors the rotational speed of the drive
wheels ⇒ page 189. If a considerable difference in revs is detected (approx.
100 rpm) in the speed of the drive wheels, e.g. when only one part of the
surface supporting the wheels is slippery, the system applies the brake to
slow down the skidding wheel so that more of the power is directed to the
other wheels. The systems works up to a speed of approx. 80 km/h. The
system will make noise while it is working.
Starting the vehicle
If one wheel has less grip and starts spinning (for instance, if one of the
drive wheels is on ice), keep pressing the accelerator gradually until the ve-
hicle starts moving. Overheating of the brakes
To prevent the brake disk of the braked wheel from overheating, the EDL
cuts out automatically if subjected to excessive loads. In this case, the vehi-
cle will continue to run and will have the same running properties as those
of another without EDL.
The EDL will switch on again automatically when the brake has cooled
down.
WARNING
● When accelerating on a uniformly slippery surface (for instance all
four wheels on ice or snow), press the accelerator gradually and careful-
ly. Despite EDL, the drive wheels may otherwise start to spin. This could
impair the vehicle's stability. Risk of accident.
● Even with EDL, you should always adjust your speed to suit the road
and traffic conditions. Do not let the extra safety features tempt you into
taking any risks when driving. Failure to do so could result in an accident.
Note
If the ABS warning lamp lights up, this can also mean there is a fault in the
EDL. Take the vehicle to a specialised workshop as soon as possible.
Traction control system (ASR)
The traction control system prevents the drive wheels from
spinning when the vehicle is accelerating. General notes
The traction control system (ASR) is one of the functions incorporated in the
Electronic Stability Control (ESC).

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The traction control system (ASR) helps the car to start moving, accelerate
and climb a gradient in slippery conditions where this may otherwise be dif-
ficult or even impossible.
How it works
The ASR works automatically, i.e. without the driver's involvement. With the
aid of the ABS sensors , the ASR monitors the speed of the driven wheels
⇒ page 189. If the wheels start to spin, the engine speed is reduced auto-
matically to match the amount of grip available. The system is active across
the entire speed range.
The ASR works in conjunction with the ABS. If a failure occurs in the ABS,
the ASR will also stop working.
In general, the ASR should be left switched on at all times. It should only be
switched off manually in particular circumstances where a certain amount of
wheel slip may be desirable. Examples:
● when driving with snow chains
● when driving in deep snow or on loose surfaces
● when rocking the vehicle backwards and forwards to free it.
The ASR should be switched on again afterwards as soon as possible.
Note
To ensure that the ASR works properly, all four wheels must be fitted with
identical tyres. The difference in size of the wheels may lead to an unde-
sired reduction in engine power. Also see ⇒ page 247.
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192Intelligent technology
Brakes
General notes
New brake pads
New brake pads do not provide optimal performance during the first
200 km; first they must be “run in”. However, the reduced braking capacity
may be compensated by pressing on the brake pedal a little harder. Avoid
overloading the brakes during run-in.
Wear
The rate of wear on the brake pads depends a great deal on how you drive
and the conditions in which the vehicle is operated. Negative factors are, for
instance, city traffic, frequent short trips or hard driving with abrupt starts
and stops.
Wet roads or road salt
In certain conditions, such as in heavy rain, or after washing the vehicle or
driving through water, the full braking effect can be delayed by moisture (or
in winter by ice) on the discs and brake pads. In this case the brakes should
be dried by pressing the brake pedal several times.
The effectiveness of the brakes can also be temporarily reduced if the vehi-
cle is driven for some distance without using the brakes when there is a lot
of salt on the road in winter. In this case, the layer of salt on the brake discs
and pads has to wear off before braking.
Corrosion
There may be a tendency for corrosion to form on the discs and dirt to build
up on the brake pads if the vehicle is used infrequently or the brakes are
not used very often.
If the brakes are not used frequently, or if rust has formed on the disks, it is
advisable to clean off the pads and disks by braking firmly a few times at a
moderately high speed ⇒
. Faults in the brake system
If the brake pedal travel should ever increase
suddenly, this may mean that
one of the two brake circuits has failed. Drive immediately to the nearest
specialised workshop and have the fault repaired. Drive there slowly and re-
member that you will have to apply more pressure on the brake pedal and
allow for longer stopping distances.
Low brake fluid level
Malfunctions can occur in the brake system if the brake fluid level is too
low. The brake fluid level is monitored electronically.
WARNING
When applying the brakes to clean off deposits on the pads and discs,
select a clear, dry road. Be sure not to inconvenience or endanger other
road users. Risk of accident.
CAUTION
● Never let the brakes “drag” by leaving your foot on the pedal when it is
not necessary to brake. This overheats the brakes, resulting in longer stop-
ping distances and greater wear.
● Before driving down a long, steep gradient, it is advisable to reduce
speed and change to a lower gear (or move the gear lever to a lower gear
position if your vehicle has automatic transmission). This makes use of en-
gine braking and prolongs the service life of the brakes. If you still have to
use the brakes, it is better to brake firmly at intervals than to apply the
brakes continuously.
Note
If you wish to equip the vehicle with accessories such as a front spoiler or
wheel covers, it is important that the flow of air to the front wheels is not
obstructed, otherwise the brakes can overheat.

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Brake servo
The brake servo assists the driver when braking
The brake servo increases the pressure you apply to the brake pedal. The
brake servo works only when the engine is running.
WARNING
Ensure the vehicle does not move while in neutral, when the engine is
stopped. Failure to do so could result in an accident.
Note
If the brake servo is not working, e.g. because the vehicle has to be towed
or because it is broken, you will have to press the brake pedal considerably
harder to make up for the lack of servo assistance.
Power steering
Power steering makes it easier to turn the steering wheel
when the engine is running. Power steering assists the driver by reducing the force needed to turn the
steering wheel.
Power steering does not work if the engine is off. In this case the steering
wheel requires much more force to turn.
If the steering is held at its turning limit when the vehicle is stationary, this
will place an excessive load on the power steering system. Turning the
steering wheel to its limit places a load on the system, which causes noise.
It will also reduce the idling speed of the engine.
CAUTION
When the engine is running, do not turn the steering wheel to its limit for
more than 15 seconds. Otherwise, there is a risk of damaging the power
steering.
Note
● If the power steering should fail at any time or the engine is switched off
(for instance when being towed), the vehicle can still be steered. However,
more effort will be required to turn the steering wheel.
● If the system is leaking or malfunctioning, please take the vehicle to a
specialised workshop as soon as possible.
● The power steering system requires a special hydraulic fluid. The fluid
reservoir is located at the front of the engine compartment on the left
⇒ page 296. The correct fluid level in the reservoir is important for the pow-
er steering to function properly. The hydraulic fluid level is checked at the
Inspection Service.
Servotronic*
The servotronic system electronically adjusts the power as-
sisted steering.
In vehicles equipped with servotronic power steering the degree of power
assistance ⇒ page 193 is adjusted
electronically according to road speed.
If a fault should occur in the servotronic system, the power steering will still
operate. The degree of power assistance will, however, no longer adapt to
different speeds. If the electronic regulating system is not working properly,
this is most noticeable when turning the steering wheel at low speeds (for
instance when parking), as more effort will be required than usual. The fault
should be corrected by a specialised workshop as soon as possible.
Safety FirstOperating InstructionsPractical TipsTechnical Specifications

200Trailer towing
Where possible, operate the trailer with the maximum permitted drawbar
load on the ball joint of the towing bracket, but do not exceed the specified
limit.
Tyre pressure
Check the tyre pressures on your vehicle, and adjust for “full load” condi-
tions (refer to the sticker listing the tyre pressures on the door pillar). It may
also be necessary to adjust the tyre pressures on the trailer according to the
recommendations of the trailer manufacturer.
Exterior mirrors
Check whether you can see enough of the road behind the trailer with the
standard mirrors. If this is not the case you should have additional mirrors
fitted. The two exterior mirrors should be fitted on folding arms. Adjust the
mirrors to give sufficient rear vision.
Headlights
Before starting a journey, check the headlight beam settings with the trailer
hitched up. If necessary, alter the height of the headlight beams by means
of the headlight range control. See ⇒ page 119.
Power supply
When you remove the ignition key, the power supply to the trailer is inter-
rupted.
Removable ball joint coupling
Vehicles with a factory-fitted towing bracket are equipped with a removable
ball joint coupling. This is stored in the spare wheel well in the luggage
compartment together with the necessary fitting instructions.
Note
If you frequently tow, we recommend you also have the vehicle serviced be-
tween services. Notes on towing
Towing a trailer involves additional attention by the driver.
Weight distribution
The weight distribution of a loaded trailer with an unladen vehicle is very
unfavourable. However, if this cannot be avoided, drive extra slow to allow
for the unbalanced weight distribution.
Speed
The stability of the vehicle and trailer is reduced with increasing speed.
Therefore, it is advisable not to drive at the maximum permissible speed in
unfavourable road, weather or wind conditions. This especially applies
when driving downhill.
You should always reduce speed immediately if the trailer shows the slight-
est sign of swaying. Never try to stabilise the trailer by accelerating.
Anticipate hazards and brake in good time. If towing a trailer with an inertia
brake, first brake gently and then harder. This will prevent brake tapping by
the trailer wheels when they lock. Select a low gear in due course before go-
ing down a steep downhill. This enables you to use the engine braking to
slow down the vehicle.
Swaying and pitching can be reduced by stabiliser aids. We recommend
having stabiliser aids installed when towing trailers with a high trailer
weight. They can be purchased and installed at a Technical Service.
Reheating
When climbing long hills in hot weather with the engine running fast in low
gear, you should keep an eye on the coolant temperature gauge ⇒ page 60.
Reduce speed immediately if the needle moves to the right end of the scale.
If the temperature warning lamp in the instrument panel should start
flashing, stop the vehicle and let the engine cool down by running it at
idling speed for a few minutes.