Hey guys hope you will be able to help me. I drive a 2016 Maxima with 35K miles.
A few weeks ago I've noticed that my fuel gauge is inaccurate (I got a full tank but the gauge was showing half) and after a couple of day the gauge went to empty and I my check engine light turned on showing the code P0463 (inaccurate fuel level readings from the fuel level sensor), After searching the web I was pretty sure it's the sending unite. I decided to buy a new aftermarket Fuel Pump with sending unite (TRQ fuel pump was cheaper than Nissan sending unite alone). That solved the fuel gauge issue but the check engine light still on and now showing code P0456 = Evaporative emission control system leak (small). I drove the car a couple of day and I made sure there are no leaks under the back seat + I checked the fuel cap.
Maybe a bad Evap Purge Valve causing the issue?
Any thoughts?

 

Start by replacing the gas tank cap. Look at the seal above the threaded area of the cap as it may be comprimised.