So these are the possible causes:
- MOST LIKELY: Bad gas cap (they go bad all the time so what you do is buy a gas cap from the following link and clear the codes, that will most likely fix your problem). Link: 10851 Fuel Cap
- The neck or any hoses going to the fuel tank. For these I recommend a leak but I can happily tell you that I never had a problem with these in all the years that I've been working in Jaguars.