ok, to open the best way is to use a tool like a dremel with a small diameter thin cut off wheel and cut the "seam" around the module with the tool making sure to not go into the module any deeper than about 5-6mm this way you wont contact the insides. you need to re-solder the pins for the big multiplug and the two pins for the pump motor plug. some of these wires are small so you need to take care. when you reassemble it use black RTV silicone or simaler so its waterproof.
as for the diagnosis it depends on if its a old or new shape v70, the older type uses volvos VST the newer v70 uses vadis/vida. a aftermarket scan tool may work although i have not used these. good luck, not many people know about this although a lot have had this problem and are charged a lot of money for what is a fairly basic re-soldering job.
steve.