I have a 2007 nissan sentra engine light is on with code P0455 I DID a smoke test AND seen smoke coming from above the gas tank how do i fix it?

First start by having the codes read and we can go from there.

large evap leak --check gas cap that it is on --look under truck at rear of fuel tank by spare tire and check the evap canister and hoses the following link will assist you
https://www.obd-codes.com/p0455 How to Fix Check Engine Light P0455 Emissions Purge Valve Replacement How to Fix Check Engine Light P0455 Emissions Purge Valve Replacement

P0455 means a gross leak detected in the Evaporative Emissions System. Some call this a "gas cap" code, because the most common cause a loose or failed gas cap. But it could be caused by any vapor leak in the fuel tank, filler neck, or anywhere else in the vapor management system. If it isn't a gas cap, you will need tol take it someplace where they have a smoke machine that can find the leak using smoke.

replace all 4 for your o2 sensors sorry i see that all the time

hi, dear friend, this is an obd2 trouble code table. it can help you understand the meaning of code.
The best way to fix a P1456 error (small evap. leak) on your Nissan is to have a "smoke machine" test done on it. This machine is hooked up to your car and pushes smoke throught the evap. system. The smoke will shoot out of the leak and indicate its precise location. You can also try getting a new gas cap and make sure that it clicks 3 times when you close it after filling your tank. Also, NEVER leave your car running when your fueling up as this can cause your "service engine soon" light to come on. The best choice however is doing the smoke test as this will elimiate any guess as to the location of the leak. Nissan dealers can perform this smoke machine test for you for about $90.00 and can save you alot of money by pin-pointing the leak so you don't keep buying parts you don't need.

The EVAP control sytem is checked by the ECM upon the first start of the day when the engine is cool and will trigger the DTC code P0445. If you have a vacuum line leak when it's cold and seals it self when it warms up then the code will stay there. After warming up the car reset the ECM to clear any DTC codes and see if any MILL shows up. IF not then there is a leak only when the system is cold so your going to have to try to do a smoke test when the system is cold.
The other thing is to check all the vacuum lines and fittings around the canister and fuel tank for any lose clamps ECT.
Good luck and keep me posted. Be glad to help you 

P0455 EVAP EMISSIONS SYSTEM GROSS LEAK DETECTED.CK GAS CAP.IF IT IS TIGHT U WILL NEED A SMOKE MACHINE TO CK THE SYSTEM FOR LEAKS

its in the gas tank but it doesnt have to be changed!!!YAY

There is a leak somewhere in the evaporative emission control system. The best way to test that is have a smoke test done on it to find out where the leak is. You'll have to call around to see if any repair shops have a smoke machine, or call a dealer.

I have never seen or heard such thing. You have a different problem. Is the "check engine light on?" Gas tanks have pressure in them on regular bases and I have never seen car sputtering because of a pressure in the gas tank.