My 2002 nissan altima starts and than it would not start up again until a couple of hours later

My 2002 nissan altima starts and than it would not start up until a couple hours later I am getting a code p0507 and p1615 what does that mean

I have a 2003 nissan altima 2.5 S sedan I got the same codes took it to autozone let them pull the codes on it P1615 means the vehicle immobilzer / anti theft system has stopped working and P0507 had 3 different possible causes 1. large vacuum leak somewhere 2. possible engine malfunction 3. electronic throttle control fault the light stayed on for two days then I stopped to get gas and then I started the car and the light was gone. I think it was the gas cap causing the vacuum leak mybe I ddidn't have it screwwed on all the way