Depressurise the system (in order to replace pressure switch No. 3)

Depressurise the system (bleed air from pressure accumulator).
CAUTION: Up to 17 bar of pressure may be present. Wear protective gloves, goggles and hearing protection.

To do this, remove (unscrew) the black protection cap on the drain valve -1- and carefully apply pressure to the valve insert using a suitable object or use a valve screwdriver Nr.164 Pos.5 to unscrew the valve insert.

Fig 1: Identifying Release Valve For System Pressure
Courtesy of PORSCHE CARS NORTH AMERICA, INC.