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 Oil Pump
Courtesy of VOLVO CARS OF NORTH AMERICA.
Undo the four bolts from the oil pump.
Carefully twist the oil pump loose. Use a screwdriver on the twist cams to free the oil pump.