What could cause me to get the evap code PO444 although my gas cap is secure. on 2008 Nissan Rogue

I have had the check engine light read 3 times: once 2 years ago and it was my gas cap. I tightened it erased the code and the light never came back on until 2 weeks ago,(2 days after the dealership put in a new transmission.) I got the same code. I refilled and super tightened my gas cap but the light will not stay off even after disconnecting my negative cable to clear the code. It initially went off after restarting it and driving it 50 miles where i turned the car off. The light came back on after restarting it after about a mile, 4 hours later. Could replacing my transmission have anything to do with this problem before I spend for the smoke test?

Asked by for the 2008 Nissan Rogue
Contact me at and I can email you TSB NTB10-018. Unless you want to spend more money.