engine PORSCHE CAYNNE S 2005 1.G Repair Manual

Shifting Gear, Traction Systems
219
Full-time all-wheel drive
With the four-wheel drive, the drive power is vari-
ably distributed to the front and rear wheels.
Power distribution and wheel speed compensation
between the front and rear axles is realised 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
achieved, even on an unfavorable road surface.
Full-time four-wheel drive ensures optimal handling
and great stability.
Safety notes!
In spite of the advantages of four-wheel drive, it is
still the driver’s responsibility to adapt 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 in-
duce you to take greater risks with your safety.
The limits set by the physics of driving cannot be
overcome, even with four-wheel drive.
Risks of accident due to inappropriate speed can-
not be reduced by four-wheel drive.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 recognises 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 be-
comes 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.

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.

Shifting Gear, Traction Systems
223
ABS
(Anti-lock Brake System)
Safety notes!
In spite of the advantages of ABS, 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 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, even during heavy braking
while cornering.
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 his driving speed to the
road conditions.Warning light
If the ABS warning lights light up in the instrument
panel and on the multi-purpose display of the in-
strument 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 brak-
ing behavior.
The ABS must be checked immediately at an
authorized Porsche dealer in order to prevent
the occurrence of further faults the effects of
which 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.
f f f

224
Shifting Gear, Traction Systems 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.
At speeds below 30 mph (50 km/h), the front
wheels can lock up in cycles during braking to
shorten the braking distance when the vehicle is
driven off-road (the wheels dig in to the surface).
If the driver needs to steer, this off-road driving
program is automatically switched off briefly to
maintain steerability.
HillholderIn selector lever positions D and M, the hillholder
function makes it easier to move off from a stand-
still 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.
Warning!
Risk of accident.
The vehicle can roll backwards if the Hillhold-
er is switched off.
fAlways apply the footbrake on slopes.
Hillholder is not active:
– In selector lever positions N and R
– In the reduced driving program and
– If not all of the wheels are touching the ground
(on difficult terrain, for example).
fPlease observe the chapter “STOPPING” on
Page 209.
Safety notes!
In spite of the advantages of the hillholder func-
tion, it is still the driver’s responsibility to adapt his
driving style and maneuvers in line with situational
conditions.
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 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
ensured.

Shifting Gear, Traction Systems
225
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 observe the chapter “TRAILER
COUPLING” on Page 194.
Danger!
Risk of accident.
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
function:
– by shifting to neutral.
– when changing gears.
– by stopping or “stalling” the engine.
Danger!
Risk of accident.
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.

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.

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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
231
Driving downhill
Danger!
There is a danger of serious personal injury
or death and risk of damage if the vehicle
should overturn.
fDo not drive over slopes at an angle to the line
of maximum gradient.
fDrive downhill slowly, with the wheels pointing
straight ahead.
fIf the vehicle starts to tilt, immediately steer in
the direction of the tilt (line of slope).
fWhen driving downhill, never let the vehicle roll
when in idle.
fUse engine braking effect.
If the engine braking effect is not adequate, gently apply the foot brake.Note on operation
fActivate Low Range. The off-road ABS is
switched on automatically.
Tips on driving
The same general principle as for uphill driving ap-
plies to downhill driving.
fDo not perform manual gear changes when
driving, and try to avoid stopping.
fAvoid high engine speeds (max. 2,500 rpm).
A special circuit of the off-road ABS permits con-
trolled brief lock-up of the front wheels so that they
can dig into the loose surface more effectively.
Locked wheels slip and can no longer be steered.
fWhen driving down steep hills on unpaved sur-
faces, brake carefully and do not start to slide.