The XJR had been parked up since August 26th (but hooked up to a battery tender), went to start her up at lunchtime at was greeted by Restricted Performance along with the Red & Amber lights, and the Engine Light. "How wonderful!" I thought to myself.

My IDS is out of commission at the moment but my little pocket scanner brought up P1254*11, looked that up in JTIS and it's soemthing to do with a fail-safe spring on the throttle body, huh?

Couldn't see any spring hanging loose (actually couldn't see one at all) so I disconnected the battery, which didn't do anything.

After several attempts clearing the code with the Autel, eventually the messages & lights went out, everything is fine now.

Damn Jaguar Gremlins! Nothing changes....

 

Can you tell me more about that? My wife's car is doing the same. We rebuilt the trans last year and it is fine. Just throws the restricted performance one in a while. Did it yesterday and the car started to run very poorly. After 30 seconds it was fine.
Thank You

 

I get this problem time to time. Comes, for about thirty seconds, and goes away. Runs poorly when it happens as well. I found mine its the plug on the mass air flow sensor. When it screws up, i have been unplugging it, clowning the pins, re-seating the pins in the harness, and re-connecting. Works every time for me. Who knows, y'all may be experiencing the same. Have AutoZone our Advanced Auto or some other part store check the code.

 

I get the restricted performance message every 10,000kms or so and my local garage just cleans the injectors and the message disappears and the performance of the car is back to square one. As I live in a dusty country, it is quite a problem and I need to service my car every 5,000kms instead of what is recommended in the manual.

 

The Restricted Performance can come up for literally dozens of reasons, that's why it's important to read the codes, and then look them up. I can tell you that all four examples in this thread so far are due to different causes.

I made a point of posting about this one with the P1254 because it had never been mentioned on the forum before.

 

Have you seen the attached TSB?

 

Thanks mate!

 

Reading between the lines of this TSB, Jaguar have no idea of the cause and their workaround is to reinstall the ECM software.

This isn't a solution and could get very costly for owners of all models as the TSB applies to XK, S, XK and X.

Graham

 

They do specify a minimum level of diagnostic software though so the reflash is probably for a later version. They also say if that doesn't work then there really is an issue.

 

if you look at the throttle body where the throttle attaches you will see two springs around the shaft just inside of where the throttle attaches to the throttle plate shaft. The TPS sensor is attached to the other end of the shaft. The inside spring balances the throttle plate with the outer spring. When the shaft gets corroded and starts sticking, you will get these errors. Use a good quality penetrating oil (not WD40) and work the springs back and forth until they move smoothly. Best of luck.