WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Control Module, DSA Warning Lamp And DSA Switch
Courtesy of VOLVO CARS OF NORTH AMERICA.
Control module (right-hand drive cars: at the left A-post), DSA warning lamp and DSA switch.