I just bought a 2013 G37XS. I took it through emissions testing a few days ago and passed. Yesterday the loose gas cap light came on. Tightened it, still on. Removed it and retightened. Still on. Bought new cap and put it on. Light still on. And FYI I did turn it till it clicked. Any ideas?

 

The light will not go off immediately. It takes several driving cycles for the computer to realize the cap is on. If you have a ODB scanner you can check if any codes are pending and clear them. As long as the cap is on tight I wouldn't be too concerned. If it doesn't go out at all after a few days then you will need to investigate further.