Couldn't find very many posts from owners with this particular problem, so hopefully someone has a suggestion.

2005 S Stype VDP, 4.2L V8. Solved issues with misfires recently with new Iridium spark plugs and 2 new ignition coils, but P0442, P0455 and P0456 persisted.

So far I've installed a new OEM gas cap, cleaned the MAF sensor with MAF sensor cleaner and replaced the Evaporative Emissions canister purge valve resonator and valve assembly.
There is no fuel smell around the car.
I've cleared the codes and they reappear after 30-40 miles of driving.

Since the P0455 is a "large leak" and P0456 is a "small leak", maybe I don't have a leak at all, but a sensor issue?

Any ideas what to check next?

Thanks!
-H

 

Get the evap system smoke tested if you can't find anything obvious like an unhooked evap line somewhere.

 

Thanks for the suggestion. I forgot to mention I did have a smoke test performed before replacing the gas cap. The test actually didn't show any leaks, but I replaced the gas cap anyway .

 

"small" means "very very small"; "large" means "detectable and bigger than small" so you may be looking for hardly any leak at all. Also, it may or may not be there all the time.

 

The link below shows the possible causes for P0445.

https://www.jaguarforums.com/forum/a...0455-p0455.pdf


It was posted by test point on the XJ forum and the link to this page is:

https://www.jaguarforums.com/forum/x...r-p0455-51210/

You seem to have done most suggestions already but it can't hurt to see this simple list to clarify your mind on the problem.

Finally below is a link to all Jaguar specific codes from Jaguar Online Club. Although you might not this need. I put it in for you anyway.

Jaguar Online Club: OBDII Fault Codes

 

Possible causes are in the S-Type part of free download JTIS. May as well have the S-Type ones!