I hope this is the right forum for this. I drive a 2002 5.4L 4x4, and my SES light came on a while back. The guy at AutoZone read the code and said it was a gas cap leak. While examining the cap and filler neck, I noticed the neck has a plastic "liner" and it was cracked. As this crack goes across the gas cap sealing surface, this is almost certainly the source of my problem. Does anyone know if the filler neck "liner" can be replaced? If not, any suggestions for repairing it?

 

You may want to try the dealer. As this is probably part of emissions warranty, it is more than likely a free fix.