Idle Control System
WARNING: This page is about a different car, the 2002 Volkswagen EuroVan, 2001 Volkswagen EuroVan, and 2000 Volkswagen EuroVan. However, it is still accessible from the selected car via links, so may be relevant.
Idle is controlled by THROTTLE VALVE CONTROL MODULE (TVCM), idle related problems will set DTCs. See appropriate SELF DIAGNOSTICS article.