I just wanted to start a thread that summarizes everyones current status of RP conditions and fixes. I realize there are several threads on here addressing this issue but if anyone who has had or has the issue can post here in a single line it would make it easier for others for troubleshooting.

I will start:

RP light somes on sporadically and car limps home, if I pull over and shut the car off and restart it, all is fine, RP goes away. Never a check engine light, most likely the leaking ECU capacitor?

 

Hi Deadboy,

Here is my contribution.

The RP message can be triggered by the engine failing to get up to operating temp, or when the ECTS or its connections are faulty. Symptoms are Temp gauge drops to cold and Restricted Performance message appears. Associated with the following fault codes:


1. P0116
Powertrain: Engine Coolant Temperature (ECT) Sensor Performance
2. P0128
Powertrain: Coolant Thermostat
This will eventually trigger the "Restricted Performance" message.

Check for:

Low coolant level -
Contaminated coolant -
Engine thermostat failure -
ECTS failure -
ECTS to ECM sense circuit: high resistance when hot or intermittent high resistance

Hope this helps.
Cheers,
Paul.

 

Well my Temp gauge stays right in the middle unless it dips for several seconds and then restores itself w/o me seeing the drop?

 

I had a situation on my 2005 XJ8 (4.2 L) where I would get the RP annunciation and then, about a minute later, the temperature guage would go from half-way (normal) to pegged-out hot in about 5 seconds. If I shut down the engine for a few seconds and re-started it, everything would reset and it would be fine for another 15 minutes, then re-occur. This only happened when cruising steadily over about 60-65 MPH. Happend regularly, over and over, but not under 60 MPH. The only code that set was P0116 - Engine Coolant Temp Range/Performance. There's a whole thread on this event over on the XJ8 forum, but the end result is that I replaced the thermostat and housing, and the problem appears to have gone away.

Cheers,

 

My car had “Restricted Performance” with the check engine light. Hard to start and idled rough. Here are the DTCs that were stored in the vehicle. P0447 P0482 P0480 P1144 and P0112. Problem is, it kept blowing fuse #12 in the engine bay fuse box which supplies B+ to the MAFS, Air/fuel ratio valve on the throttle body, ECM side of the cooling fan relay and the EVAP purge valve. Turned out to be two seperate issues. The wiring loom was chaffing against the chasis in the rear next to the gas tank causing to wires to short out. The other issue required a new Evap (part #LJB1525AB).

 

I had the dreaded RP just after I picked my XKR up, turned back around back to garage and reset everything with Snap-On diagnostic, turned for home again and all OK.
Thing is the car had been standing and the battery had run flat so we had to charge the battery for half an hour or so to get it started so I guess my problem was the low state of charge in the battery.
hope that helps
rrosscoe

 

Check your fuses. I had a string of problems a few years back. It was very hard to diagnose as the problem only occurred in mountainous areas and we live in very flat Chicago - but it was a real road trip spoiler. The local Chicago dealer even replaced the supercharger cooler based on an error code.

Happened later on another road trip and local dealer in Colorado found only a blown fuse (on supercharger cooler) and haven't had any issues since they replaced it. The spend a day or two trying to figure out what caused the fuse to blow and found nothing. Made me wonder about local dealer that changed the supercharger cooler under warranty. I've had an unopened pack of spare fuses in the trunk since then.

 

We just had it along with a code showing left cylinder bank lean condition, and accompanying CEL. Turned out the rubber boot between the MAF and intake manifold had a bunch of perforations along the bottomside. My independent Jag mechanic who troubleshot this said he sees it a lot but not usually on a car with such low mileage as ours (38K). But he also said some mechanics try to clean the MAF and some powerful solvents puddling there would cause this.

 

LSIMON or anyone:

Where is the supercharger fuse located? It states in the book passengers side bulkhead like fuse 12? Not sure what bulkhead is..lol.

 

I think that's it, it is the intercooler for the supercharger. I don't think the supercharger itself has a fuse so it will work until it becomes overheated then an error is recognised and engine goes into RP. When you restart the car AFTER it has cooled then it works fine until overheated again. It starts knocking just before it goes into RP as the intake gases are too hot causing premature ignition. I think I recall the dealer saying it is actually the anti-knock sensors forcing the RP when it the system couldn't compensate enough. In our case it was becoming overheated when going through mountainous hilly areas but no errors were being recorded when in flat territory as the supercharger wasn't taxed as much or as often - that made it difficult to diagnose.

The passenger bulkhead fuse box in in the engine compartment in front of the passenger side. My manual covers the location of the 5 fuse boxes and lists the fuses.

 

thanks!!!!!

my 15A supercharger cooler fuse was blown!
you saved me a ton of $$$ and hassles!
Awesome!
Replaced it and kept some spares in my glovebox.'I wonder WHY it blew??????

 

It's happened to me this morning! RP!
My car sounds like 20 year old transit van and it's 2 months out of warranty. Not happy. I've booked into stratstones tomorrow to find out what the codes are so I can get it sorted! Grrr.
I'm not a mechanic and I can already feel my bank account being emptied of money!
I'll keep you updated!

 

Hi all:

Great thread to start. Just had my 1st last night. Had the car about 2000 miles now. 99xk8 conv. In the process of ordering auto engin code reader so no codes. After over night it stopped doing it. But going to clean the tbody connectors, wheel sensors and maybe check the abs module for solder joints. But most seem to lean towards tbody connectors as I understand the wheel sensors will not give rperf.
Will return to this thread later the summer when I get my code reader, if and when this happens again

Howard