Where is the camshaft position sensor located on 2002 Volvo s80 t6 and how many is needed?

They are located on the top of the engine opposite side of the engine belts and at the end of the double overhead cam. The are located inside black plastic housings, just look for the electrical leads going to them.

They rarely fail, if you are getting cam position sensor codes, make sure the timing belt hasn't slipped.