This is ridiculous. I was getting this message and would go unfasten my gas cap and put it back on tightly. Then I would get the message and repeat the process several times within a short time span before the message would come on again. So I think I will get a new gas cap and it will have a better seal then the original one so I order a new cap. Now I am going through the same thing again. What is it with these cars? You sneeze and they get sensitive. I have the same problem with the Engine coolant low message but I will address that in another post.
What can I do on this gas cap situation?
Thanks,
Bill

 

The "check gas cap" comes on when the system senses that the fuel tank is not holding pressure. If the new cap doesn't fix it, then there may be a leak elsewhere, most likely in one of the tubes leading into the tank or the gasket around the pump or sensing unit's entry into the tank. (see below)

 

Jaguar had a TSB for the gas cap replacement it was 508 or 509. The reason you will not be able to find it is that Jaguar has classified it as being complied with. The purpose for the TSB was that the gas cap was hard to close resulting in a leak causing false check engine light and at times gas odor. Not sure that it applied to your car but I would call and find out. I got mine for my 99xk8 in the mail after my first service at the local Jaguar dealership. I hope this helps! Gus

 

Sure it wasn't a recall Gus? I remember getting a gas cap for either our 95 XJ12 or 98 XJ8 when they were out of warranty.

 

Called Jaguar today to confirm my info prior to posting. However, you might be right!