OK, back being a pest. I am getting a P0456 code -- small leak -- but though I am getting the "check your gas cap" warning, I am not getting a check engine light. Why is that? Thanks.

 

A bit of background: many an owner would go to a tech saying "the MIL was on but now it's off, what was wrong?"

So, a code stays recorded internally if the fault is not currently present. The MIL is on if the fault is currently present.

If the fault stays away for a long time (40/80 warm ups), on our era cars it is deleted.

That's for an actual fault.

The other kind is a pending code - i.e. the fault has occurred but not often enough (or in the same situation) to be made an actual fault (with MIL).

I suspect you've the second kind.

Do look up the code for your car model i.e. Jaguar's data - because it lists all the know causes (which may not be solely the one you put).

 

Thanks JagV8. Where can I find this Jag data base to look up my code?

 

Hi scrannel,

I am attaching the most complete DTC Summaries guide that I have for the 4.2L cars. It's for the 2004 model year XJ, but should be applicable to your 2008 S-Type. Here are the definition and possible causes of P0456:




A common issue I have dealt with on 4.2L cars (S-Type, XJ, XK) is a charcoal canister vent valve that has failed in the open or partially open position, so since you've apparently checked the purge valve, the canister vent valve would be my next suspect. The vent valve, sometimes called the solenoid in the service documentation, is located on the underside of the vehicle near the rear/fuel tank, so it is subject to water ingress. It is part 9 in the diagram below:

Cheers,

Don

 

Thanks Don. One more question (before I crawl under the car) is this solenoid in plain sight or hidden under the bottom cover? Thanks.

 

I can't remember for certain on the S-Type, but I think it may be above the rear axle. The most recent one I replaced was on a 4.2L XK, and it was easily accessible next to the charcoal/carbon canister. The canister is a black plastic rectangular container, so it's usually easy to find.

Cheers,

Don

 

Thanks!

 

This site's Stickies & JagRepair.com - Jaguar Repair Information Resource

 

Thanks!