Hello, Everyone...
Looking for help trouble shooting the "RESTRICTED PERFORMANCE" error message I get with my 2008 Jaguar XK (4.2L normally aspirated) when it is driven for more than 10 minutes in sport mode with lots of paddle shifting (as if driving on a track). Car's performance is reduced while in this mode (revs and power limited). If I pull over, take it out of sport mode, turn it off and restart it, the error goes away and car then runs normally again in standard shifting mode. Never happens unless in sport mode with lots of paddle shifting. Anyone with a similar experience and solution? Dealer seems to have no idea what to do. Thanks!

 

You need to get the dealer (or, since the dealer seems to be useless, a Jaguar independent) to read the fault codes stored in the ECM to see what the cause of the restriction is. That is something I would expect a mechanic to do as the very first step of diagnosis. If that has been done and the dealer is telling you there are no codes, perhaps buy a cheap OBDII reader so you can look for codes yourself when the problem is being exhibited. They won't be as comprehensive as with the Jag diagnostic system, but it will provide some clues.

My guess would be: something to do with air/fuel mix (restricted airflow, air leaks, fuel starvation, knocking, etc.), because that's the sort of problem that tends to be 'amplified' when you run at higher RPM. The fault may be real, or it may just be a borderline-faulty sensor. But there are plenty of other possible causes, which is why getting the codes is absolutely vital.

 

+1 and at least check battery is working a lot more than adequately.