Mercedes-Benz 2008 S550 Operator's Manual page 451

Controls in detail
Driving systems
Park Assist is also switched off when you
set the automatic transmission to P or
switch off the engine.
While the transmission is in neutral
position N, Park Assist is switched off if
you secure the vehicle in place with the
electronic parking brake.
The Park Assist system monitors the sur-
roundings of your vehicle with four sensors
in the front bumper and two sensors in the
rear bumper.
450
Range of the sensors
The sensors of the Park Assist system are
integrated in the front and rear bumpers.
Make sure that the bumpers are clear of
dirt, ice and slush in the area of the sen-
sors, as otherwise, Park Assist may not
function properly, see "Cleaning the Park
Assist* system sensors (USA only)"
( page 590).