2004 PORSCHE CAYENNE ESP

182
Driving and Driving Safety
Warning!
In spite of the advantages of PTM or four-wheel dri-
ve, it is still the driver’s responsibility to adapt her/
his driving style and maneuvers in line with road
and weather conditions, as well as the traffic situ-
ation.
The increased safety that is provided should not
induce you to take greater risks with your safety.
The limits set by the physics of driving cannot be
overcome, even with PTM or four-wheel drive.
Risks of accident due to inappropriate speed
cannot be reduced by PTM.Porsche Traction Management (PTM)Porsche Traction Management is a full-time all-
wheel control system designed to influence the
longitudinal and lateral dynamics. It is closely
linked with the Porsche Stability Management
(PSM) system:
PTM ensures the best possible power distribution
to the four driven wheels at the front and rear
axles. The system realizes this optimal traction by
intervening in the lock control function of the trans-
fer case and rear differential. PTM is active at all
times and, unlike the PSM, cannot be switched off.Advantages of PTM
– Obvious improvement in traction, driving
stability and steering ability of the car.
– Vehicle is more manageable when driven at its
performance limits.
– Improved straight-ahead tracking and stability.
– The aforementioned features allow for a
sportier setup of the running gear.
– The TCS and ABD provide even better traction
for all wheels.
Full-time all-wheel drive
With the four-wheel drive, the drive power is
variably distributed to the front and rear wheels.
Power distribution and wheel speed compensation
between the front and rear axles is realized with a
transfer box.
Distribution of the drive power depends on the
wheel speed difference between the two axles.
The transfer box always controls power distribu-
tion in such a way that optimal propulsion is achie-
ved, even on an unfavorable road surface.
Full-time four-wheel drive ensures optimal handling
and greater stability.Automatic brake differential (ABD)
The ABD system controls the front and rear axles
separately. If one wheel of an axle starts to spin,
it is braked so that the other wheel on the same
axle can be driven.
The ABD recognizes different driving states, and it
features control strategies adapted to these
states. In situations in which little propulsive power
is required, such as when the car moves off on a
level gravel surface, traction control already
becomes active at low engine speeds. If great
propulsive power is required, e.g. when moving off
on an uphill slope or for rapid acceleration, the
ABD is adapted accordingly.
A special off-road program is used in Low Range
mode.
Traction control system (TCS)
The traction control system prevents the wheels
from spinning by adjusting the engine power,
thereby ensuring good lane-holding ability and a
stable driving behavior.10_Cayenne_21_KW17.book Seite 182 Donnerstag, 9. April 2009 3:33 15

Driving and Driving Safety
183
Porsche Stability Management (PSM)PSM is an active control system for stabilization of
the vehicle during extreme driving maneuvers. It
operates together with the Porsche Traction
Management (PTM) system.
PSM makes use of both the ABD and TCS
systems, as well as the known functions of the
anti-lock brake system (ABS) and engine drag
torque control system (MSR).
Warning!
In spite of the advantages of PSM, it is still the
driver’s responsibility to adapt her/his driving style
and maneuvers in line with road and weather
conditions, as well as the traffic situation.
The increased safety that is provided should not
induce 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 (load-alteration effect) when the
driver releases the accelerator pedal or brakes
on bends. This compensation functions up to
the maximum lateral acceleration.
– PSM actively stabilizes the vehicle as required
during dynamic driving maneuvers (e.g. rapid
steering movements, during lane changes or
on alternating bends).
– Improved braking stability on corners and on
different or varying road surfaces.
– Improved brake functioning and reduced
stopping distance in the event of emergency
braking.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 (steering angle)
– 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
actual 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
Tiptronic in order to stabilize the vehicle.
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184
Driving and Driving Safety The events below inform the driver of PSM control
operations and warn him to adapt her/his driving
style to the road conditions:
– The multi-functional information light in the
instrument panel lights up.
– Light in the PSM Off button flashes.
– 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.
In order to achieve full vehicle deceleration,
foot pressure must be increased after begin-
ning of the brake pedal pulsing.
Examples of PSM control operations
– If the front wheels of the vehicle drift on a
corner, engine power is reduced and the rear
wheel on the inside of the corner is braked if
necessary.
– If the rear of the vehicle swings out on a
corner, the front wheel on the outside of the
corner is braked.– Brake system prefilling:
The brake system is prepared for possible sub-
sequent emergency braking if the accelerator
pedal is released suddenly and quickly.
The brake system is prefilled and the brake
pads are already applied gently to the brake
discs.
– Brake booster:
In the event of an emergency braking operation
where the pedal force is insufficient, a brake
booster provides the braking pressure neces-
sary for maximum deceleration at all 4 wheels.
Combined use of PSM and PTM/PTM Plus
In order to ensure optimal stabilization of the ve-
hicle, the center differential lock (PTM) and possib-
ly the rear differential lock (PTM Plus) are also
opened when PSM interventions occur.
Tip on driving
When PSM is switched off, wheel-specific brake in-
terventions 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.
In order to improve driveability on difficult terrain,
the response of the off-road PSM is less sensitive
in the low speed range when the vehicle is opera-
ted in the Low Range off-road driving program.
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 passing. This is
also the case for downshifts on a slippery road.
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186
Driving and Driving Safety Collapsible spare wheel
fNever switch the PSM off when driving with a
collapsible spare wheel.
To w i n g
fFor information on towing:
Please see the chapter “TOWING” on
Page 342.
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.
Switching PSM back onfPress PSM OFF button A.
PSM is switched on after a short delay.
The light-emitting diode in the button and the
multi-functional PSM light on the instrument
panel go out. A message is shown on the multi-
purpose display of the instrument panel.
ABS
(Anti-lock Brake System)
Warning!
In spite of the advantages of ABS, it is still the
driver’s responsibility to adapt her/his driving style
and maneuvers in line with road and weather
conditions, as well as the traffic situation.
The increased safety that is provided should not
induce you to take greater risks with your safety.
The limits set by the physics of driving cannot be
overcome, even with ABS.
Risks of accident due to inappropriate speed can-
not be reduced by ABS.
ABS ensures:
–Full steering control
The vehicle remains steerable
–Good driving stability
No skidding due to locked wheels
–Optimum braking distance
Shorter stopping distances in most cases
–Lock prevention
No flat spots on the tiresFunction
The decisive advantage of ABS is in the driving
stability and maneuvrability of the vehicle in
hazardous situations.
ABS prevents locking of the wheels during full
braking, on almost all road surfaces, until shortly
before the vehicle stops.
The ABS begins to control the braking process as
soon as a wheel shows a tendency to lock.
This controlled braking process is comparable to
extremely rapid cadence braking.
The pulsating brake pedal and a “rattling noise”
warn the driver to adapt her/his driving speed to
the road conditions.
fIf full braking should be necessary, press the
brake pedal all the way down throughout the
entire braking procedure, regardless of the
pulsating pedal. Do not ease up on pressure
applied to the pedal.
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Driving and Driving Safety
187
Warning light
If the ABS warning lights light up in the instrument
panel and on the multi-purpose display of the
instrument panel while the engine is running, the
ABS has switched off because of a fault.
In this event, the braking system will operate with-
out lock prevention,as in cars without ABS.
fAdapt your driving style to the changed
braking behavior.
fThe ABS must be checked immediately at an
authorized Porsche dealer. This is necessary
in order to prevent the occurrence of further
faults whose effects cannot be defined.
The ABS control unit is adjusted for the approved
tire dimensions.
The use of tires with non-approved dimensions can
lead to different wheel speeds, causing the ABS to
switch off.
Off-road ABS
(ABS in Low Range program)
When Low Range is active, an ABS specially
matched to off-road driving is activated automati-
cally.In the event of braking on loose ground, the per-
missible slip values for ABS braking are increased
so that the off-road braking distance is reduced
(wheels dig into the surface).
If the driver needs to steer, this off-road driving
program is automatically switched off to maintain
steerability.
Hillholder -
moving-off assistant on vehicles with
Tiptronic SIn Tiptronic selector lever positions D and M, the
hillholder function makes it easier to move off
from a standstill on an upward slope when the
engine is running. The driver does not have to
apply the brake.
The hillholder thus makes moving off on slopes
easier.
Danger!
Risk of accident, resulting in serious perso-
nal injury or death.
The vehicle can roll backwards if the Hillhol-
der is switched off.
fAlways apply the footbrake on slopes.Hillholder is not active:
– In Tiptronic selector lever positions N and R
– In the limp-home mode and
– If not all of the wheels are touching the ground
(on difficult terrain, for example).
Warning!
In spite of the advantages of the hillholder func-
tion, it is still the driver’s responsibility to adapt
her/his driving style and maneuvers in line with
situational conditions.
The increased safety that is provided should not
induce you to take greater risks with your safety.
The limits set by the physics of driving cannot be
overcome, even with the hillholder function.
Driving at the limits should be avoided, e.g., on icy
slopes or on slippery surfaces. In this and similar
cases, the support of the hillholder function is not
guaranteed.
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188
Driving and Driving Safety
Porsche Drive-Off Assistant –
Moving-off assistant on vehicles with
manual transmissionThe Porsche Drive-Off Assistant enables the driver
to move off on upward slopes. The vehicle must
have sufficient road contact to use this feature.
The Porsche Drive-Off Assistant is available for
slopes starting at approximately 5%.
fPlease see the chapter “TRAILER COUPLING”
on Page 230.
Danger!
Risk of accident, resulting in serious perso-
nal injury or death.
When moving off on a slippery surface (e.g.,
on icy or loose surfaces), assistance by the
Porsche Drive-Off Assistant is no longer
assured. In this case, the vehicle could slip.
The limits set by the physics of driving cannot
be overcome, even with the Porsche Drive-
Off Assistant. The responsibility for moving
off on upward slopes is still the driver's,
despite the Porsche Drive-Off Assistant.
fAlways adjust your driving style to the driving
conditions and vehicle load, use the footbrake if necessary.Moving off with Porsche Drive-Off Assistant
1. Hold the vehicle securely with footbrake or
parking brake on the slope.
The engine must be running.
2. Fully depress the clutch pedal.
3. Engage one of the gears used to ascend in the
direction of travel (1st gear or reverse).
4. While keeping the clutch pedal depressed,
release the footbrake or foot-operated parking
brake.
The vehicle is held on the slope.
5. Move off as usual.Note on operation
The Porsche Drive-Off Assistant ceases to func-
tion:
– By shifting to neutral.
– When changing gears.
– If the engine is not running.
Danger!
Risk of accident, resulting in serious perso-
nal injury or death.
If the Porsche Drive-Off Assistant ceases to
function, the vehicle will no longer be held on
a slope.
fHold the vehicle with the footbrake.
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192
Driving and Driving Safety Indication of selected level
The selected level is displayed by light-emitting
diodes beside the rocker switch (illustration).
The corresponding light-emitting diode beside the
rocker switch flashes during the control process.
The light-emitting diode is continuously lit after the
control process.
The level change is also indicated on the multi-
purpose display of the instrument panel.
Exceptions
Automatic changes from normal level to low level
and back are not indicated on the multi-purpose
display of the instrument panel.
Warning messageVarious messages are indicated on the multi-pur-
pose display of the instrument panel if there is a
system fault or if the compressor switches off due
to overload.
fFor further information on warning messages
on the multi-purpose display:
Please see the chapter “OVERVIEW OF
WARNING MESSAGES” on Page 149.
fAdapt your driving style to the changed condi-
tions.
fConsult an authorized Porsche dealer in order
to remedy a system fault.
fIf the overload-protection function causes the
compressor to switch off, wait for a time until
it has cooled down. The system will function
again as soon as it has cooled sufficiently.
The warning message appears when the control
system is switched off and when the collapsible
spare wheel is being filled. This does not indicate
a fault.
The warning message will go out once these
procedures have been completed.
Raising vehicle with the jackWhenever it is necessary to jack up the vehicle:
fManually set normal level and then switch off
level control.
Switching off level control
1. Switch ignition on.
2. Push rocker switch forward for 5 to
10 seconds.
A message is shown on the multi-purpose
display of the instrument panel.
The vehicle can now be raised.
Switching level control back on
1. Switch ignition on.
2. Push rocker switch forward for 5 to
10 seconds or
3. Drive forward with the vehicle.
Level control switches on automatically.Transporting the vehicles on car trains,
ferries and car transportersfTie the vehicle down only at its wheels.
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194
Driving and Driving Safety
Porsche Dynamic
Chassis Control (PDCC)FunctionPorsche Dynamic Chassis Control (PDCC) is a sys-
tem for roll stabilization of the vehicle body when
driving. Driving comfort and driving safety are im-
proved by active intervention of the anti-roll bars
on the front and rear axles.
No separate controls are available for the PDCC
system.
After selection of a running-gear setup in Porsche
Active Suspension Management (PASM):
–comfort
–normal
–sport
PDCC automatically activates the corresponding
on-road driving program.
fFor information on selecting a running-gear
setup:
Please see the chapter “PORSCHE ACTIVE
SUSPENSION MANAGEMENT (PASM)” on
Page 193.
PDCC automatically activates the off-road driving
program if Low Range reduction is switched on.fFor information on switching Low Range
reduction on and off:
Please see the chapter “DRIVING PROGRAMS
FOR ON-ROAD AND OFF-ROAD DRIVING” on
Page 177.
Warning messageA warning message appears on the multi-purpose
display of the instrument panel if there is a system
fault.
fFor further information on warning messages
on the multi-purpose display:
Please see the chapter “OVERVIEW OF
WARNING MESSAGES” on Page 149.
fAdapt your driving style to the changed
conditions.
fConsult an authorized Porsche dealer in order
to remedy the fault.
Checking hydraulic fluidRegular checking and changing of the hydraulic
fluid takes place as part of servicing.
Further important information on “Maintenance”
can be found in a separate chapter.
fPlease see the chapter “CAR CARE
INSTRUCTIONS” on Page 270.
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