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Operation
How the ABS works
If
one of
the wheel
s turns too slowly in rela-
tion to the vehicle's speed, and is close to
locking, the system will reduce the braking
pressure to this wheel. The driver is made
aware of this control process by a pulsating
of the brake pedal and audible noise. This is
a deliberate warning to the driver that one or
more of the wheels is tending to lock and the
ABS control function has intervened. In this
situation it is important to keep the brake
pedal fully depressed so the ABS can regu-
late the brake application. Do not “pump”.
If you brake hard on a slippery road surface,
the best possible control is retained as the
wheels do not lock.
However, ABS will not necessarily guarantee
shorter braking distances in all conditions.
Braking distance could even be further if you
brake on gravel or on fresh snow on a slip-
pery surface.
Control lamp
The control lamp lights up for a few sec-
onds when the ignition is switched on. It
goes out again after the system has run
through an automatic test sequence.
There is a fault in the ABS if:
●
The control lamp does not light up when
the ignition is switched on.
●
The control lamp does not go out again af-
ter a few seconds.
●
The control lamp lights up when the vehicle
is moving.
The vehicle can still be braked in the normal
way, without the ABS function. Take the vehi-
cle to a specialised workshop as soon as
possible.
If there is a fault in the ABS, the ESC* and the
tyre pressure control lamp will also light up.
Brake system fault
If the ABS warning lamp lights up together
with the brake warning lamp , there is a
fault in the ABS function and in the brake
system ›››
.
WARNING
●
The anti-lock br
ake system cannot defy the
laws of physics. Slippery and wet roads are
dangerous even with ABS! If you notice that
the ABS is working (to counteract locked
wheels under braking), you should reduce
speed immediately to suit the road and traffic
conditions. Do not let the extra safety fea-
tures tempt you into taking any risks when
driving.
●
The effectiveness of ABS is also determined
by the tyres fitted ››› page 210.
●
If the running gear or brake system is modi-
fied, the effectiveness of the ABS could be se-
verely limited.
WARNING
●
Befor
e opening the bonnet, read and ob-
serve the warnings ››› page 198, Working in
the engine compartment.
●
If the brake system warning lamp should
light up together with the ABS warning lamp
, stop the vehicle immediately and check
the brake fluid level in the reservoir
››› page 206, Brake fluid. If the brake fluid
level has dropped below the “MIN” mark you
must not drive on. Risk of accident. Obtain
technical assistance.
●
If the brake fluid level is correct, the fault in
the brake system may have been caused by a
failure of the ABS system. This could cause
the rear wheels to lock quickly when you
brake. This could cause the rear to break
away. Risk of skidding. Stop the vehicle and
seek technical assistance.
Electronic differential lock (XDS)*
When taking a curve, the driveshaft differen-
ti
al
mec
hanism allows the outer wheel to turn
at a higher speed than the inner wheel. In
this way, the wheel that is turning faster (out-
er wheel) receives less drive torque than the
inner wheel. This may mean that in certain
situations the torque delivered to the inner
wheel is too high, causing the wheels to
spin. On the other hand, the outer wheel is
receiving a lower drive torque than it could
transmit. This causes an overall loss of lateral
156
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