Along with the exploding charcoal canisters, a real common issue for the R50's (mine included) is the valve dying since it's in such an exposed location. If the valve is stuck open, it makes it impossible for the EVAP system to run a pressure check, so it throws a SES code (P0446, maybe some others too). The bolts holding the valve onto the canister are just screwed into plastic female threading, so it can be a pain in the ass to get the valve off (grinder, hacksaw, etc...). But, if you can get those bolts to give, just hook a 12V up to the valve and see if it closes, if not give it a hit of WD40 like Dank suggested and hope that fixes things, but otherwise gotta replace the whole assembly.