My name is John Flanagan.
I live in northern VA.

I drive an '06 XK8 convertible - about 75K miles - 4.2 liter / 6 speed automatic - which I've had since it was new and has treated me pretty well.

I've been reading posts on this site for years and learned a lot of good stuff about my Jag.

And now a troublesome mechanical problem has prompted me to join and actively seek advice.

My problem is very similar to one I read about on this site:
In Oct 2013, "rflexible" wrote about multiple gearbox faults in an '03 XK8 over a period of 6 weeks.
They were preceded by "harsh shifting" from first to second gear.

In my '06, I've had two "gear box fault" messages.
First one in early June was preceded by several weeks of gradually slower shifts from 2nd to 3rd and then occasional, unexpected banging into gear.
This was severe enough to jolt the vehicle and occurred at relatively low vehicle speeds (say 20 to 40 mph) and light throttle position.
Finally got gear box fault message while driving 75 miles from home and vehicle went into limp home mode.
Got it to nearest Jag dealer for evaluation. Mechanic called next day to say
diagnostics showed multiple codes (P0782, P1111, P1582 among a total of 21 total).
HOWEVER - he could find nothing wrong with the trans - no leaks or other signs of failure and no problems at all during a road test.
He further said the trans in my Jag was a very good one, and widely used in European vehicles.
He said there was nothing to fix. He recommended I take it home and hope problem didn't happen again.
He did note that there were "reprogramming" steps that could be taken for the engine and transmission control modules, but recommended against it unless there were future problems.
I drove home and then drove the car most of 2,000 miles over next 3 months without incident.
Then about a week ago, entire process repeated itself - except that - gear box failure message and limp home mode initiation occurred in my own driveway instead of 75 miles away.
After sitting for two days, car again ran fine on short trips.
Have talked to two local shops about a repair strategy. They admitted they could only guess at cause (and solution) unless I brought the vehicle to them while in limp home mode (easier said than done).

So here I am.
Would be most grateful to hear from anyone who can offer me some insight and suggestions about next steps.
Either way, thanks for reading my tale of woe.

 

Wow, seems like a nice and honest assessment from the dealer. Rosenthal, maybe?

The vanilla answer is to wait until it happens again, and make sure to collect all codes. This is a bit tough as some of the codes reset at the next restart. Maybe the dealer service department can provide these codes (all of them). Or they might be in your paperwork.

Second vanilla answer is to check the battery. Folks have reported long lists of codes after starting a car with a spent battery. Check the battery date, have it load tested, or just change it.

Third vanilla answer is to start looking into a transmission service. The fluid/filter is 10 years old. This is a not-so-simple procedure that involves draining, replacing filter and refilling (with the car running) until a temperature is reached. There is debate also as to what fluid to use (ZF or Ford Mercon SP).

From memory, do you recall seeing an ABS/Traction Control light as well? If you do, there is an off chance the reluctor ring is loose on the driver side wheel hub. This is, at best, a wild guess, and something to check only after making sure the battery is up to par.

Best of luck, keep us posted.

 

When gearbox fault error was followed by Limp Mode it turned out to be the TPS on the throttle body on my 2002 XJ8 SE. It was the only fault it ever had in 240,000 miles! All Jaguar owners should have a spare body on the shelf - it is the most likely cause of peculiar error messages.

 

To jimforrest

Thanks for your response.

At one of the shops I consulted after second occurrence of my problem, a mechanic did say that they had repaired a Jag with a similar problem and cause was indeed the throttle body (sending erroneous signals of some sort to the transmission module).

Replacement isn't cheap. I wonder if you found that there was a way to confirm that the throttle body was your problem before committing to replace it?

 

To fmertz,

Thanks for these recommendations.

Let me add some more information.

Got a complete list of the DTC's from the Jag Dealer (Jim Coleman in Clarksville, MD) who checked out my Jag after first episode of transmission trouble:
C1286 (ABS), B1969 (ATC), B2334 (BPM), U1041 (BPM), B1595 (BPM), U2012 (BPM), B1438 (BPM), B2323 (DDM), B2327 (DDM), B1236 (DDM), P0782 (ECM), P1111 (ECM), P1582 (ECM), U1260 (IP), U1261 (IP), B2323 (PDM), B2327 (PDM), B1236 (PDM), U1041 (SLM), P0110 (SLM), B24BD (SLM).
Many of these seem completely unrelated to the transmission problem, but that's the complete list.

Battery is only two years old and shows no signs of weakness, but - as you suggest - I will have it checked when I take the Jag in for evaluation.

Ditto the transmission service - will have this done when I take Jag in for evaluation.

Re ABS, checked my maintenance records and came up empty - did have a couple of episodes of DSC warning lights, but these were caused by related equipment failure and were repaired.

Thanks again for taking an interest in my problem.

 

Using Jaguar's list of DTCs and their causes, P0782 is a 2-3/3-2 gear load fault. Possible causes listed are Engine Control Module Torque signal fault or a transmission mechanical failure.

P1582 indicates that the limp home has initiated a Flight Data record to be taken and stored

P0110 is not listed!

Either P1111 - all engine management OBD diagnostic monitor drive cycles HAVE BEEN COMPLETED or P1000 - all engine management OBD diagnostic monitor drive cycles HAVE NOT BEEN COMPLETED, will always be shown.

Without checking them all one by one, those other Bxxxx, Cxxxx and Uxxxx codes look remarkably similar to those that I get whenever I call up All Codes after a reasonable running period. However, they do not appear if I ask for Current Codes. Over seven years I have learnt to live with them!

If you can find a shop that can extract the flight data, it could give some guidance to the conditions when it occurred. Similarly, a high end scanner can get the torque signal and monitor it, though that might be awkward if it's a long time between failures.