I have had this code for over a year now. I've gone through 3 different gas caps including the OEM from Nissan and I still get this code. Anyone know of common problems that would cause this light to come on? I know there are a ton of possibilities but theres got to be a few things that are known to fail that cause this code.

 

0705 is the jackpot code. Check all the EVAP hoses, connections, canister, valves ect. A shop manual will help you follow the system through and check it's components.
The valve by the canister does tend to get stuck, usually it throws a code specifically for that. You might start there, maybe you'll get lucky.

 

Purge control valve?