Diagnostic Functions: General
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2009 Volvo S60, 2008 Volvo S60, 2007 Volvo S60, 2006 Volvo S60, and 2005 Volvo S60. However, it is still accessible from the selected car via links, so may be relevant.
The control modules have a built-in diagnostic system, Volvo Diagnostics, which continuously monitors its own system as well as the input and output signals.