My son's 2000 S40 shows a P0441 - which suggests either a gas cap issue (the rubber gasket does have cracks so I think I'll replace that), evap system (vacuum line) hose issues or a faulty evap cannister purge valve. Question is where is the purge valve located? I see its PN 9470775... $35 at Tasca but will inspect the hoses first.

 

As a follow up & close out, a dealer parts diagram gave me the clue I needed. The evap purge valve is located under the radiator cover shroud on the drivers side up top. 15 minute change - remove the plastic cover piece, the two clips that hold the lines, the sensor connector and a clip to hold in place...