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32
Brake assistant
Investigations in accident research have
shown, that the majority of drivers fail to ade-
quately actuate the brakes in an emergency
situation.
This results in insufficient brake pressure
being generated to achieve maximum vehicle
deceleration.
This lengthens the braking distance.During emergency braking, the brake assist-
ant aids the driver by increasing the brake
pressure automatically, to a level exceeding
the locking limit.
The ABS (
A
nti-lock
b
raking
s
ystem) is thus
quickly brought into the operating range,
which enables a maximum vehicle decelera-
tion to be achieved.
Brake servo pressure sensor G294 is used for
detection of emergency braking.
Time [t]
Pressure [p]
For this purpose, the pressure increase gradi-
ent (pressure build-up with respect to time) is
evaluated and, if necessary, the brake assist-
ant is activated.
SSP254_093
Emergency braking
Normal braking distance
Pressure sensor G294
Running gear
SSP254_092
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54
5 V/Div.=10 ms/Div.
0 T
Electrical system
In the "highline" version of the vehicle electri-
cal system control unit, only the 21 watt
filament of the two-phase bulb for the brake
and rear light is used.
With lights switched on and non-actuated
brakes, the power rating is reduced to 5 watts
by a pulse-width modulated signal via the
vehicle electrical system control unit J519.
Thus a self-diagnosis/driver information
system (FIS) is possible for the second rear
light.
A defective brake light would be indicated in
FIS.
In vehicles with the "highline" version, national
lighting regulations can be adapted via
coding.For non-plausible condition of the rotary
light control, the side lights and low beam
are switched on automatically by the vehi-
cle electrical system control unit in the
"highline" version.
SSP254_080
Measuring equipment
DSORecorder operation
Photo
Channel A
Channel B
Measuring
mode
Cursor 1
Cursor 2
Multimeter
Help Print
PositionTime/Div.
Trigger mode
Skip
Brake not actuatedBrake actuated
Rear lights on:
5 V/Div.=2 s/Div.
0
Electrical fault finding
In certain lighting circuits, an open-circuit
voltage measurement using the Multimeter is
not possible, as the semi-conductor elements
are clocked until the circuit is again closed.
For defective bulbs which are operated via the
vehicle electrical system control unit J519, no
permanent fault storage is effected, but only
for the period of the fault.
This means that the fault memory must not
be erased after changing a defective bulb.
Measuring equipment
DSORecorder operation
Photo
Channel A
Channel B
Measuring
mode
Cursor 1
Cursor 2
Multimeter
Help Print Ve h i c l e
self-diagnosis
Position Time/Div.
Reversing lamp on:
1 - bulb illuminates
2 - bulb failure
3 - clock frequency of power output
1
2
3
SSP254_052
