My 1999 XKR has a restricted performance light on sometimes after 0.5mile and sometimes 10 miles . 3 garages have used their compatible diagnostic equipment and can find no faults . Any ideas ?

 

How old is your battery? Failing batteries often throw spurious OBDII codes and dashboard warning messages....

 

Thanks however the battery was replaced in September this year.

 

Have you measured your battery voltage with the engine off and again with the engine running? If not, do so and post the values here....

Remember that any battery can fail at any time....

 

I was getting a "restricted performance" warning and the car was "surging". I cleaned the MAF and TB and replaced the fuel filter, that fixed the issue. I think my fuel filter was the original. I don't recall if I was getting any error codes.

 

I'm skeptical that you would get a restricted performance warning with no MIL and no DTCs stored or pending. Maybe they only scanned the ECM and no other modules and weren't using a "fully" jaguar compatible scanner, merely OBDII? There are numerous transmission faults that can trigger a restricted performance, for example. My obdlink adapter with Torque on my phone for example can't read the transmission controller, abs controller, etc etc, I have to use my iCarsoft . I just find it exceptionally unlikely that you'd get the message without any codes being stored. Judging from descriptions in the Jag DTC manuals and my own experience, and the various diagnostic procedures in the workshop manuals, once a fault is stored it will remain until cleared even if the triggering condition is transient and is no longer observed.

 

I'd get a good OBD tool, plug it in, get used to it, then as soon as the fault occurs see what the tool has.

Even an elm327 _might_ be enough but a better tool would be wiser. The site/forum has info on them.

Not IDS/SDD! You don't want to try driving around with that unless you're especially keen (or mad).

 

I’m skeptical too, but that’s my current reality. And I think I’m using the same OBD-II tool as you, the icarsoft LR v1.0 .

no codes are being stored. Will check out battery voltage tomorrow. The restricted performance comes and goes….

 

Re- boot ecu, pull battery cables and hold together for 10 min. Drains surface memory in ecu. Re-install cables. Turn on ignition but don’t start. Let ecu go thru the system scan. Then start. You will need to re- set radio so you need your code. Mine was written in my jag bookst came with car. Then re- set your windows. This little trick solved all of my problems! No more codes and re-sets and runs great !

 

Different car, but my STR once threw RP with no codes (at that time), I think (guess) because it wasn't sure what to flag. I restarted the engine after a short stop and no further issue. Unsolved.

If it keeps happening I'm really surprised if no codes - but do check for pending ones just in case.