Possible cause of fault

WARNING: This page is about a different car, the 2006 Porsche Cayenne, 2005 Porsche Cayenne, 2004 Porsche Cayenne, and 2003 Porsche Cayenne. However, it is still accessible from the selected car via links, so may be relevant.

Short circuit to ground in the wiring of pin 46 of the level control module (electrical fault in electric circuit)
Short circuit to B+ in the wiring of pin 46 of the level control module (electrical fault in electric circuit)
Open circuit in the wiring of pin 46 of the level control module (no signal/communication)
Selector switch faulty
Level control module faulty