Porsche Cayenne Turbo Driver Manual page 188

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:
– 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 Tiptronic in
order to stabilise the vehicle.
188
Driving and Driving Safety
The events below inform the driver of PSM control
operations and warn him to adapt his driving style
to the road conditions:
– The multi-functional information light on the
instrument panel flashes.
– Light in the PSM Off button flashes.
– Hydraulic noises can be heard.
– The vehicle decelerates and steering-wheel
forces are altered as PSM controls the brakes.
– Reduced engine power.
– The brake pedal vibrates and its position is
changed during braking.
In order to achieve full vehicle deceleration,
foot pressure must be increased after the
brake pedal has begun vibrating.
Examples of PSM control operations
– If the front wheels of the vehicle drift on a
bend, the engine power is reduced and the
rear wheel on the inside of the bend is braked
if necessary.
– If the rear of the vehicle swings out on a bend,
the front wheel on the outside of the bend is
braked.
– Brake system prefilling:
The brake system is prepared for possible
subsequent emergency braking if the acceler-
ator 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 operation of PSM and
PTM/PTM Plus
In order to ensure optimum stabilisation of the
vehicle, the centre differential lock (PTM) and
where appropriate also the rear differential lock
(PTM Plus) are also opened when PSM interven-
tions 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.