2005 PORSCHE CAYENNE S differential

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.

222
Shifting Gear, Traction Systems
Switching off PSMfPress button A.
PSM is switched off after a short delay.
With PSM switched off, the PSM warning light
in the instrument panel and the information
light in the button are lit.
During braking, the vehicle is stabilised even
when PSM is switched off.
One-sided spinning of the wheels is prevented,
even with PSM switched off.PSM should always be switched on during
“normal” driving.
H o w e v e r, i t c a n b e o f a d v a n t a g e t o s w i t c h o f f P S M
temporarily in exceptional situations:
– On a loose surface or in deep snow
– When “rocking the vehicle free”
– When using snow chains.
When the PSM is switched off the slip monitoring
function of the Tiptronic is also deactivated.
Information light
– The light indicates a control operation, includ-
ing when PSM is switched off (brake control in
the event of one-sided wheel spin).
Warning light
– The warning light in the instrument panel lights
up in combination with the indicator light in the
button for a lamp check when the ignition is
switched on.
– Together with the information light in the
button, the warning light indicates that PSM is
switched off.
– A fault is indicated by the warning light in the
instrument panel and an indication on the multi-
purpose display of the instrument panel. PSM
is out of order.
Please have the fault remedied at an autho-
rized Porsche dealer.Collapsible spare wheel
fNever switch the PSM off when driving with a
collapsible spare wheel.
To w i n g
fPlease observe the chapter “TOWING” on
Page 350.
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.
Switching on PSMfPress button A.
PSM is switched on after a short delay.

228
Shifting Gear, Traction Systems
Driving systems for off-road drivingSpecially adapted driving programs or power-
transmission and running-gear control systems
are available for off-road driving:
– Off-road program Low Range
–Off-road PSM
–Off-road ABS
– Center differential lock
– Rear differential lock
fPlease observe the chapter “POWER-TRANS-
MISSION AND RUNNING-GEAR CONTROL SYS-
TEMS” on Page 217.
Before driving offTires
fCheck tread depth and tire pressure.
fCheck for damage and remove any foreign ob-
jects (e.g. stones) from the tread.
fReplace missing valve caps.
Rims
fReplace dented or damaged rims before
driving off road.
After driving off roadOff-road driving places a greater burden on the ve-
hicle than does normal driving on roads.
We recommend inspecting the vehicle after off-
road driving. Potential damage poses an accident
risk and impairs driving comfort. Damage on the
car is recognised in good time if the car is
checked.
Warning!
Car damage poses an accident risk for the
vehicle occupants and other road users.
fIn cases of doubt, have your vehicle checked
by your authorized Porsche dealer.
fExamine tires for signs of damage such as
cuts, tears, bulges or foreign objects stuck in
the tread. Replace a damaged tire if neces-
sary.
fHave any damage to your vehicle repaired by an authorized Porsche dealer without delay.

230
Shifting Gear, Traction Systems
Uphill driving
Danger!
Danger of serious personal injury or death
and risk of damage if the vehicle should
overturn.
fDo not turn around when driving uphill.
fIf it is not possible to climb a gradient, the car
must be backed down in reverse gear.
fDo not drive over embankments or slopes at
an angle to the line of maximum gradient.
fIf the vehicle starts to tilt, immediately steer in
the direction of the tilt (line of slope).
fWhen driving uphill, never let the vehicle roll
backward when in idle or not in gear.
Exclusive use of the footbrake is too risky in such situations.Note on operation
fActivate Low Range before taking extreme up-
ward or downward gradients.
Tips on driving
fDo not perform manual gear changes when
driving, and try to avoid stopping.
fAvoid high engine speeds (max. 2,500 rpm).
Traction on uphill slopesNote on operation
fActivate Low Range and engage differential
locks if necessary.
Tips on driving
fWhen driving uphill, go easy on the accelerator
and make sure that wheels have sufficient trac-
tion (don't spin).
fAvoid high engine speeds (max. 2,500 rpm).
fDrive slowly.

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).

234
Shifting Gear, Traction Systems
Crossing obstacles
Caution!
Risk of damage to the underbody and chas-
sis components if obstacles are traversed
improperly.
fAlways bear in mind the ground clearance of
your vehicle.
fSlowly drive over the middle of tree trunks,
boulders or other obstacles with one of the
front wheels.
fCross the obstacle with the rear wheel in the same way.
Note on operation
fActivate Low Range.
Tips on driving
fHave your passenger direct you if necessary.
fAvoid high engine speeds (max. 2,500 rpm).
fDrive slowly.
Driving on sandNote on operation
fActivate Low Range and engage differential
locks if necessary.
Tips on driving
Loose sand is an especially tricky surface for off-
road driving.
You can often become stuck in sand within
minutes if you do not drive correctly in such
situations.
fDrive at brisk pace and do not stop under any
circumstances. This will reduce the chance of
the car becoming bogged down.
fFollow existing tracks – provided that they
have not been covered by blown sand, are not
too deep and the car's ground clearance is
sufficient.
Please observe the chapter “GROUND CLEA-
RANCE” on Page 366.
fAvoid high engine speeds (max. 2,500 rpm).

Shifting Gear, Traction Systems
235
When driving on slopes with soft sand on vehicles
with Tiptronic S:
fUse the manual select mode M in addition to
the Low Range program.
If your vehicle becomes stuck nevertheless:
Do not spin the wheels. Instead, use branches,
mats or similar items to provide adequate traction
so that you can drive out of the critical area.
Track rutsOther vehicles leave ruts in many off-road courses
or gravel roads.
fPlease observe the chapter “GROUND CLEA-
RANCE” on Page 366.
Caution!
Risk of damage to the vehicle floor when
driving through ruts that are too deep.
fAlways bear in mind the car's ground clear-
ance.
fDo not drive over ruts that are too deep.
Note on operation
fActivate Low Range and engage differential
locks if necessary.
Tips on driving
fIn cases of doubt, drive with one wheel on the
strip of grass.
fAvoid high engine speeds (max. 2,500 rpm).
fDrive slowly.

314
Practical Tips, Minor Repairs 22 Rear differential lock30
23
Rear differential lock, disengageable anti-roll bars
10
24 Tire pressure monitoring system5
2526Porsche Stability Management, passenger airbag deactivation, brake pedal switch, instrument panel, engine control unit,
airbag control unit, steering column module1027282930313233
Steering wheel heating, steering column module
15
34 Passenger compartment monitoring, seat heating5
35
Low beam, high beam
15
36 Vehicle electrical system control unit10
3738 Brake lights1039
Relay activation, heated rear window, seat heating
5
40 Instrument panel5
41
Porsche Entry & Drive
15
42 Panorama roof30
43
Subwoofer
30 No. Designation Rating in A