Hi, I have an intermittent problem with my Feb 2007 registered 4.2 XKR coupe with approx 40k miles.
It’s very intermittent, like once every 2 or 3 months or maybe 60+ journeys, it goes from running fine, can be half an hour into a journey or more, and it just stops running, multiple errors flash up, and it loses all power, I mean it can move but 5mph at best, it tends to happen under (medium) acceleration, but with no warning.
When I read the codes I get a large selection (attached last 2 reports) just about every module (apart from things like audio) have some errors - I clear them, and I’m back off and running perfectly for another couple of months!
when it fails and I pull over, restarting the car doesn’t fix it, the engine is lumpy like it’s running in 2 cylinders! Press accelerator and nothing happens. As soon as it’s cleared it’s fine.

I checked all the connections to modules and fuse board that I ca find, and can’t see any obvious issues, it’s all clean and dry.
Any suggestions? I’m at a bit of a loss, so far I have been lucky with it happening at times I can easily pull over, but one time it was on the motorway on-ramp, on to a “smart” motorway with no hard shoulder!

thanks, Paul.

 

Thanks for providing the data. But many of these items do not include a Jaguar fault code. Would you gave SDD and prepare that report?
This is an interesting situation, though a burden for you. Is the ECM overheating? A grounding issue. I need more data.

 

I don’t have access to SDD, when it fails I need to clear the codes or get the car collected on a trailer, so I keep a code reader with Jag software in the car, what sort of codes would I expect to see different to those in the uploaded report (they start end of page 2) ?
I visually checked earths and connectors, I don’t see any obvious issues, the odd thing is how intermittent it is, for example I drove a few hundred miles recently with no issue, then the last time it failed I was probably 30mins into a short journey, overtaking a truck uphill!

 

It appears I didn't look far enough into your document/ Do you have the XK Service Manual. Its in a sticky at the top of the forum.
Some of those U codes are pretty dire. And for fear of being ripped by those that ignore the Service Manual, review the first thing stated in the list of items to check...

 

I had a look through the service manual, difficult when you have so many codes, it doesn’t point to any single thing, it points to everything! So probably a can bus problem or earth issue of some sorts, I think Im going to have to knuckle down and go through it bit by bit!

 

You don't have a cheap OBD reader permanently plugged in to the diagnostic port by any chance? My '07 XKR started cutting out intermittently and I eventually traced it to that.

On one occasion the car was totally dead and I had to unplug the battery to get it to start again.

 

No, I only connect to the odb when it fails, to read and clear the codes. It’s the kind of error collection that would be be attributed to the battery if it didn’t actually work fine 99% of the time.

 

When it happens does your CEL illuminate?

 

When it happens as I’m driving, I get no CEL, but it scrolls through error messages including; engine systems fault, cas system fault, DSC unavailable, park brake fault, and it won’t rev past about 1500 rpm, when I switch it off and on, then I get the check engine light too.

 

Exact same thing happened to me a couple weeks ago on an on ramp accelerating hard in 3rd and all of a sudden like restricted performance but allot worse. But I got nothing no codes no cel nothing. Shut off motor restarted and life is good. Puzzling. My agm battery is on the way out so I figured that was the issue.

 

After running the car for at least 15 minutes, carefully touch each battery terminal. If one or both is very hot to the touch, you have a bad battery cable. It is fairly common for them to fail at the crimp and cause faults across the entire vehicle.

 

Mine has happened probably 5 times over 8 months, 4 times it involved I would say medium acceleration (once on an on-ramp) but it has thrown errors every time, the battery is about a year old so I counted that out, especially as it’s so intermittent, but the next response about battery cable, that’s a good shout.

 

Thats a good shout 👍 the battery is about a year old, but I didn’t fit it, I will get on that!

 

I've had these same symptoms several times over the last three years. I might use the car for months without it happening and then, out of the blue I get restricted performance and errors. I've watched the faults popping up when it happens and I see things like the park brake and CATS failure popping up first.
So far, I've been able to pull over, turn off the car, and wait for a minute. I restart and it starts just fine, but with CEL illuminated, so I turn off and restart again. CEL doesn't come back on and everything is fine.
It does seem like a bad ground or something causing reset with the rear control module maybe, then things cascade from there.
Changed battery earlier this year. The voltage is definitely better and it's still happened about three times.
The only common thing I think I've noted is that it seems to happen when I've accelerated (not even hard) from a stop and the trans is shifting.
I have 126K miles on mine and I recently switched out the trans with a used one that has 59K a few weeks ago. I am waiting to see if that change helps, but the problem is so intermittent I won't know for a while.

 

Well I guess I’m glad it’s not just me, but wish I had found an answer.
I think I’m starting with battery terminals and earths, going to check, clean and reconnect everything I can get hold of. If I got more than 2 months without problems, I will post an update.

 

I also had some very strange intermittent problems on my 4.2 XK 2007.
After trying different solutions, and even though I had my battery checked (they said is was working OK) I decided to change the battery for a new one.
From then on the problems were solved but, after some time without running, the problems came back. I had to keep the battery fully charged from then on to avoid problems.
Perhaps this experience may help you.

Marcoshilario

 

Thanks, I’m starting to think it could be the same issue! Even though I drive it regularly, it probably needs to be on a battery conditioner!

 

Unfortunately this is a common occurrence on our cars. From my experience I have found out that a weaker battery as if when it was sitting without a tender for a few days will do it. Also what I have found out that when I had an Agm battery overall voltage in the system was lower and I was having more issues with this shutdown. Switched back to regular lead acid battery And car is much better.
Another issue that I am suspecting is a worn out alternator, it still puts out voltage as it should but occasionally I hear alternator whine and voltages drops, so I suspect it could also be a contributing factor. We'll find out when I replace an alternator..

 

Had something similar with one of the Land Rovers, after extensive diagnosis determined in was a faulty alternator generating erratic voltage which in turn caused every module in the vehicle to fail. Fitted a new alternator and all's well.

 

Thats actually a great find. OP definitely has an electrical problem. I had the same thing on a Testarossa. Turns out the connection ring on a cannon plug to an ECU was cracked and under hard acceleration, the connection would become loose. I would go over the car while its idling and jiggle every connector I could find including cleaning all grounding straps and battery terminals. Try to get it to fail. Oh, and load test the battery and buy a quality scanner.