Fault code 21

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2004 Porsche Boxster, 2003 Porsche Boxster, 2002 Porsche Boxster, 2001 Porsche Boxster, and 2000 Porsche Boxster. However, it is still accessible from the selected car via links, so may be relevant.