2005 PORSCHE CAYENNE S brakes

Shifting Gear, Traction Systems
205
D - Automatic selection mode (in the road
driving program)The functions of selector lever positions Dand M
differ in the on-road program, High Range, and in
the off-road program, Low Range.
fUse selector lever position D for “normal” driv-
ing.
The gears are shifted automatically according
to the accelerator position and speed.
Depending on the way the vehicle is driven and on
the resistance (e.g. uphill), the gear-changing
points are shifted towards higher or lower engine-
speed ranges. Movement of the accelerator,
driving speed, longitudinal and lateral acceleration
and the road profile all have an influence on the
gear-changing characteristic.
When PSM is switched off, transmission gear
changes are done at higher engine speeds.
Unwanted upward shifts, e.g. before bends, are
prevented by swiftly releasing the accelerator ped-
al.
Depending on lateral acceleration, upward chang-
es on bends are not made until the engine-speed
limit is reached.
During braking, and depending on the amount of
deceleration, the Tiptronic changes down earlier.
For subsequent cornering, the right gear is en-
gaged when pressure is applied to the brakes be-
fore the bend.The bend is taken in the right gear, and when you
accelerate out of the bend you do not have to
change down.
Moving off
In 2nd gear, the vehicle moves off with the throttle
only slightly open. Move off in 1st gear with the
throttle open wider or when the engine is cold.
When PSM is switched off, the car generally
moves off in 1st gear.
Shifting gear on the steering wheel
By shifting gear with the rocker switches on the
steering wheel, you can temporarily change from
automatic selection mode D to manual selection
mode M.
Advantages
– Shifting down before bends and on entering
built-up areas.
– Shifting down on downward slopes (engine
braking).
– Shifting down for brief spurts of acceleration.
– Selecting 1st or 2nd gear for moving off.
The manual selection mode remains engaged:
– For cornering (depending on the lateral accel-
eration) and overrunning,
– When the vehicle is stationary (e.g. at a junc-
tion).The system leaves manual selection mode:
– automatically after around 8 seconds
(unless car is cornering, overrunning or
stationary),
– if you depress the accelerator to kickdown.
Temporary change-down
Precondition
– Speed is higher than approx. 33 mph
(54 km/h).
fDepress accelerator quickly.
The Tiptronic changes temporarily to the sport-
iest gear-changing map, i.e. to the highest pos-
sible gear-changing points. Correspondingly,
the transmission shifts down immediately by
one, two or three gears.
Ending the function
fRelease the accelerator markedly (by approx.
25%).
f f f

220
Shifting Gear, Traction Systems
Porsche Stability Management (PSM)PSM is an active control system for stabilisation of
the vehicle during extreme driving maneuvres. It
operates together with the Porsche Traction
Management (PTM) system.
PSM makes use of both the ABD and TCS sys-
tems, as well as the known functions of the anti-
lock brake system (ABS) and engine drag torque
control system (MSR).
Safety notes!
In spite of the advantages of PSM, it is still the driv-
er’s responsibility to adapt his driving style and
maneuvres in line with road and weather condi-
tions, as well as the traffic situation.
The increased safety that is provided should not in-
duce you to take greater risks with your safety.
The limits set by the physics of driving cannot be
overcome, even with PSM.
Risks of accident due to inappropriate speed
cannot be reduced by PSM.Advantages of PSM
– Best possible traction and lane-holding ability
in all driving situations – even on road surfaces
with varying friction.
– The system compensates for undesired vehi-
cle reactions (Ferraria effect) when the driver
releases the accelerator pedal or brakes on
bends. This compensation functions up to the
maximum lateral acceleration.
– PSM actively stabilises the vehicle in the event
of under and oversteering during dynamic
driving maneuvres (e.g. rapid steering move-
ments, during lane changes or on alternating
bends).
– Improved braking stability on bends and on dif-
ferent or varying road surfaces.Readiness for operation
PSM is switched on automatically every time you
start the engine.
Function
Sensors at the wheels, brakes, steering system
and engine continuously measure:
–Driving speed
– Direction of travel
– Lateral acceleration
– Longitudinal acceleration
– Rate of turn about the vertical axis
PSM uses these values to determine the direction
of travel desired by the driver.
PSM intervenes and corrects the course if the ac-
tual direction of motion deviates from the desired
course (steering-wheel position):
It brakes individual wheels as needed. If neces-
sary, PSM additionally influences the engine power
or the gear-changing characteristic of the Tiptron-
ic in order to stabilise the vehicle.

Shifting Gear, Traction Systems
221
The events below inform the driver of PSM control
operations and warn him to adapt his driving style
to the road conditions:
– The information light in the instrument panel
lights up.
– Hydraulic noises can be heard.
– The vehicle decelerates and steering-wheel
forces are altered as the PSM controls the
brakes.
– Reduced engine power.
– The brake pedal pulsates and its position is
changed during braking.
However, it is possible at any time to achieve
full vehicle deceleration by increasing the foot
pressure slightly.
Examples of PSM control operations
–Vehicle understeers:
If the front wheels of the vehicle drift on a
bend, engine power is reduced and the rear
wheel on the inside of the bend is braked if
necessary.
–Vehicle oversteers:
If the rear of the vehicle swings out on a bend,
the front wheel on the outside of the bend is
braked.Combined use of PSM and PTM/PTM Plus
In order to ensure optimal stabilisation of the
vehicle, the center differential lock (PTM) and
possibly the rear differential lock (PTM Plus) are
also opened when PSM interventions occur.
Tip on driving
When PSM is switched off, wheel-specific brake
interventions and the traction control system
(TCS) are also inactive.
The automatic brake differential (ABD) remains on.Off-road PSM
(PSM in Low Range program)
When Low Range is active, an off-road PSM
specially matched to off-road driving is activated
to enhance traction.
At a speed below 22 mph (35 km/h), the terrain
PSM intervenes later if the vehicle should under-
steer and thereby improves steerability in Low
Range.
If the brakes are highly stressed, the automatic
brake differential (ABD) switches itself off to
protect the brakes. It remains deactivated until the
brake system has cooled sufficiently.
Engine drag torque control
In conditions of excessive slip, the engine drag
torque control system prevents all driven wheels
from locking up when the car is overrunning. This
is also the case for downshifts on a slippery road.

226
Shifting Gear, Traction Systems
Engine Braking Support
(Assistance when heading downhill)The Porsche Down-Hill Assistant is an assistance
system which helps the driver at slower downhill
driving up to approx. 12 mph (20 km/h), e.g., on
steep slopes or on wintry mountain roads.
As long as the gas pedal is not used when trav-
eling downhill, the Porsche Down-Hill Assistant is
active and brakes the vehicle.
The braking ability of the Engine Braking Support
is affected by slippery surfaces (e.g., on icy or
loose surfaces), like all brakes.
If road grip is lost on one or more wheels, the
system brakes the wheels which have good road
contact.
Conditions:
– The gas pedal must not be used when
travelling downhill.
– The speed must not exceed 12 mph
(20 km/h).
– The selector lever position D or Mmust be
engaged.
Warning!
Risk of accident. Reduced braking ability on
a slippery surface.
fAlways adjust your driving style to the driving situation.
Tip on driving
The Porsche Down-Hill Assistant is active when
driving downhill either forwards or backwards.
Checks on test standsPower measurement
Power measurements on roller test stands are not
approved by Porsche.
Brake tests
Brake tests must be carried out only in High Range
and on plate-type test stands or roller test stands.
The following limit values must not be exceeded
on roller test stands:
– Testing speed 4.7 mph (7.5 km/h)
– Test duration 20 seconds
Parking brake test
Parking brake tests on the brake tester must be
performed only with the ignition switched off and
the selector lever in position N.
Balancing wheels on the vehicle
During finish balancing of the wheels, the entire ve-
hicle must be lifted and the wheels must be free to
turn.

Shifting Gear, Traction Systems
227
Off-Road DrivingPlease read this chapter carefully before driving
off road with your Porsche.
The information provided will familiarise you with
the special advantages of your vehicle, allowing
you to arrive at your destination safely every time.
We recommend practicing on less rugged terrain.
Vehicles with SportDesign package
Warning!
Risk of damage. On vehicles with Sport-
Design package, front, rear, and side
member trim are painted and pulled down
lower. Off-road driving can seriously damage
these trim parts.
fWhen driving off-road, make sure these parts
are not damaged.
fMake sure there is sufficient clearance
between obstacles and the underside of the
vehicle.
fAvoid driving through water.
fDo not use side member trim as a running board.Maintenance note
Please bear in mind that off-road driving subjects
all vehicle components to considerably more wear
than normal use, making professional inspection
and maintenance after each use a vital precondi-
tion for functioning and safety.
Grains of sand, dirt particles and other abrasive
materials entering the brakes can cause exces-
sive wear or unpredictable braking action.
Rules for off-road drivingfEnsure vehicle is equipped with approved all-
terrain tires.
fPlease observe the chapter “GROUND CLEA-
RANCE” on Page 366.
fActivate Low Range.
fStow or fasten luggage and loads securely.
Please observe the chapter “LOADING INFOR-
MATION” on Page 195.
fIf unknown terrain is obscured from view, ex-
amine it on foot first and traverse it with ex-
treme caution.
This way, obstacles are easier to recognise
and damage to the vehicle is avoided.
fAlways drive with the engine running.
Steering assistance is provided only with the
engine running.
fDrive slowly and uniformly.fAlways make sure that the wheels touch the
ground.
fBefore driving through water, check the water
depth, the condition of the surface beneath it
and the speed of the water.
fLook out for obstacles such as boulders,
holes, tree stumps or ruts.
fAlways keep the sliding/lifting roof or
Panorama roof system and the side windows
closed while driving.
fDo not depart from marked routes or paths.
fRespect Nature.
Always obey off-limits signs.

232
Shifting Gear, Traction Systems
Water crossingfPlease observe the chapter “GROUND CLEA-
RANCE” on Page 366.
Danger!
Danger of drowning if water enters the vehi-
cle. Risk of damage to the engine and acces-
sories if water penetrates.
fBefore driving through water, check the water
depthA, water speed and the condition of the
surface beneath it.
The water must not be deeper than 20 in./
50 cm (22 in./55.5 cm for vehicles with level
control and height adjustment).
fCheck the door sills and rubber seals before
starting to drive.
fDo not drive through deep or rapidly flowing
water.
Deep or rapidly flowing water, e.g. mountain
streams, can cause the car to deviate from the
desired path.
fAvoid a "bow wave" by driving at an appropriate
speed.
fNever open the doors when driving through wa-
ter.Soiling can impair the braking action.
fCheck and clean the brakes if they have been
soiled.
Danger of steering assistance failing during
a long journey in the water if the drive belt
slips.
fIf the steering assistance fails, more effort will
be required to steer.
Danger of damaging electrical systems
fAvoid driving through salt water.
Notes on operation
fActivate Low Range.
fSwitch the air conditioner off.
fSwitch the headlights off.

Shifting Gear, Traction Systems
233
Tips on driving
fAvoid high engine speeds (max. 2,500 rpm).
fDo not perform manual gear changes when
driving, and try to avoid stopping.
Moving off in the water can be difficult due to
the high resistance and the loose surface in-
volved.
fStart the water crossing at a shallow place at
walking speed.
fAfter checking the body of water, take the
shortest path through it.
fNever drive into the water at high speed. The
resulting “bow wave” could damage the engine
and its accessories.
fAdjust your driving style to the unfamiliar sur-
roundings.
fCross the body of water slowly and at a con-
stant speed.
fNever turn around when crossing a body of wa-
ter.
fIf it is not possible to cross the body of water,
the car must be backed out of it in reverse
gear.
The servo pump and alternator can fail if the car is
driven through water for an extended period.
fIf the servo pump fails, substantially more
force will have to be exerted in order to steer. Maintenance note
The car requires a special check after the water
crossing.
fRemove mud from the tire tread.
fBriefly brake the brakes dry after driving
through the water.
HumpsfPlease observe the chapter “GROUND CLEA-
RANCE” on Page 366.
Note on operation
fActivate Low Range and engage differential
locks if necessary.
Tips on driving
fJust before reaching the hump, ease off the ac-
celerator slightly and use the car's momentum
to cross the hump. This will prevent the car
from jumping over the hump and landing on the
following downward slope at an excessive
speed.
fAvoid high engine speeds (max. 2,500 rpm).

Maintenance, Car Care
251
Brake-Fluid LevelfPlease observe the chapter “EXERCISE
EXTREME CAUTION WHEN WORKING ON YOUR
VEHICLE” on Page 242.
fUse only new (unused) Original Porsche brake
fluid.
Warning!
Brake fluid is hazardous to your health, and
may be fatal if swallowed.
Brake fluid also attacks paintwork.
fKeep brake fluid out of children's reach.
fImmediately rinse off spilled brake fluid with
clean water.
fIf brake fluid gets into your eye, immediately
rinse with clean water for a few minutes. Then
see a doctor immediately.
fPlease note all the information on the refill container of the brake fluid.
Checking the brake-fluid levelThe reservoir for the hydraulic braking system is
located in the engine compartment.
1. Rotate the turn-locks 90°anti-clockwise
(arrow) with a screwdriver and remove the
cover.2. Check brake-fluid level at the transparent
reservoir.
The fluid level should always lie between the
MIN and MAX marks.
A slight decrease in the fluid level due to wear and
automatic readjustment of the disc brakes is
normal.
If, however, the fluid level falls markedly or below
the MIN mark, the braking system may have devel-
oped a leak.
fPlease have the braking system checked im-
mediately at an authorized Porsche dealer.