My 2010 nissan versa went in two weeks ago to have the fuel pump regulator replaced. Apparently it was a recall and they fixed it. A few days later my check engine light came on and i got it checked the code was P0456 which has to do with the gas cap not being on. I tightened it and the light went off after a day. Three days later the check engine light is on again....i just bought a brand new fuel cap and the light is still on...can anyone think of anything else? Pretty odd that nissan was the last to touch my fuel system and now the check engine is on...