Operation ofthe ABS system
A wheel speed sensor ismounted toeach ofthe
four wheels. Ifwheel lock-up ofeither ofthe front
wheels orthe rear wheels issensed duringbrak-
ing, thebrake pressure isadjusted automatically
until thewheel nolonger slips.Thebrake pressure
is regulated foreach frontwheel individually and
for both ofthe rear wheels together.
On aroad surface whichisslippery ononly one
side, therear wheel whichisbraking onthe slip-
pery surface determines thebrake pressure which
will beapplied equallytoboth rearwheels. Thisen-
sures thatdirectional stabilityismaintained. How-
ever, ifbraking forcesapproach thewheel lock-up
point forallwheels (panicbraking) theABS system
will intervene toprovide arapid rythmic braking.
The proper operation ofABS isperceived bythe
driver asapulsating brakepedalinconjunction
with audible noiseandperhaps somevibration.
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Ifyou experience thesesensations whiledriv-
ing oraroad surface withquestionable trac-
tion, reduce vehicle speedappropriate forthe
prevailing roadconditions.
The functional readinessofall the main electrical
components ofthe ABS ischecked byan
electronic monitoring systembothbefore and
while youdrive. •
Warning lightUSA
• Warning lightCanada
When theignition isswitched onthe ABS warning
light willlight upwhile thesystem iselectronically
interrogated andgoes outwhen theengine is
started ifthe check isnot yetcomplete.
If the ABS warning lampfailstogo out, thisindi-
cates thatABS hasbeen deactivated duetoa
fault. Ifthe warning lightsinthe instrument panel
and on-board computer lightupwhile youaredriv-
ing, this indicates thatafault hasoccurred. Inboth
cases, normal braking, asinvehicles withoutABS,
is still retained.
The ABS system should,however, beexamined at
an authorized Porschedealerimmediately topre-
vent theoccurrence offurther faults.
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Ifthe ABS system becomes inoperative, take
your vehicle toyour authorized Porschedealer
immediately.
A
Warning!
The control unitofthe ABS brake system is
set forstandard tiresize. Ifnon-standard
tires areinstalled, thecontrol unitmay mis-
interpret thespeed ofthe vehicle, because of
the variant dataitreceives fromthesensors
on the axles.
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Use only tiremakes andtypes tested by
Porsche.
Controls,Instruments
