Hey Guys,

I wanted to break this out into it's own thread because dammit, when I am looking for info on a certain topic, it gets buried in weird and useless search names costing hours of searching only to find - well nothing at all?

My 2003 Jag XK8 started to develop some real issues after changing my fluid and filter in the transmission. I changed the fluid because I had just bought the car at 120K and it had that 2nd to 1st gear bump going on. After some reading on here I changed the filter and used Mercon SP fluid to top it up. All seemed well in the beginning as the bump started to subside but after a spirited run on the freeway and a kickdown from 6th to 5th, I threw my first Transmission Fault Warning / Limp Home. I got off the freeway and after turning the car off and on again, the fault went away and I puddled home. Since then, it's been one hurdle after another trying to locate the source of the issues. They are all on here if you search posts by me. I finally went ahead and bought myself the JLR-SDD software so I could more accurately troubleshoot the issue. Yesterday, I put the car back up on jackstands (the worlds biggest PITA to check transmission fluid level) and using the software, accurately set the level on the fluid. Truth is that it was pretty much good anyway. I should also mention that I changed the fluid twice. First to get rid of most of the original dark stuff and then again to dilute whatever was left in the torque converter.

So I went into this with all kinds of gear ratio and sorted DTC's logged. At first there was only one for 5th gear but eventually I got several of them. I hooked up the software and was able to monitor pretty much whatever I wanted to and set to looking at the pressure sensors on the valve body of the transmission. The software states that the readings are in milli-amps and the range should be between 0 and 250. It didn't take long before I saw that several of mine were way over that. I have a couple at 50mA but others that are over 500 and even 900 mA. This could be attributed to a number of things but the results are shown in the video I have posted to YouTube. This video has me driving the car while recording the pressure sensor activity. At first I am just stopped and cycling through the gears. Then I start going through different routines. You will figure out when it is that I am slowing down, turning, etc. because of the gear position display. I expect changes in the pressure sensor voltages but these appear to be all over the place.

The next video I shot was to show that all of my wheel speed sensors were functioning properly.

And then finally a video to show input and output speeds + transmission fluid temp.

If I was a betting man, I would have to assume there is something up with the valve body but I have no clue yet. I am going to send these videos to a ZF tech and see what he/she says.

A word of caution!!

So because I had the software all hooked up and was understanding things pretty well, I figured it wouldn't be an issue to go ahead and clear the transmissions adaptive data and start fresh.

I hooked everything up and put a battery charger on the car. I measured at the battery terminals and saw a constant 13.4v being delivered so I felt I was good on that end. Battery is pretty new as well so I felt confident.

Navigated my way to the adaptive clear and reset feature and after a little deep breath, hit the go button and things starting moving right along - or so I thought! I sat and sat and I sat for over an hour and without any sort of status bar, I had no idea what, if anything was happening. I searched everywhere on the net trying to figure out how long this process should take and could not find a damn piece of info anywhere. So at 90 minutes I figured something was not happening and I cancelled out of the reset. So the software locked up and I had to task manager it closed and disconnected the Mongoose cable from the car. Figured since it was only an adaptive reset, I would be fine - wrong!

After I cycled the key, Transmission Fault came up on the dash and I was now permanently in limp home mode. Nothing fixed it and that's when I got the lump in my throat. The only blessing was that I felt I may be dealing with a pooched transmission anyway and after some research, discovered that on ebay, used TCM's could be had for 100.00. Not too bad and not like the car had caught fire or anything. After about 30 minutes of frustrating searches, I brought the car into the car port and decided to have another go at it. Maybe I could get through this without a complete catastrophe?

Interesting things noticed on the second attempt?
The first thing I noticed after rebooting the laptop and getting everything set up again was that the battery icon in the top right had turned green. On the first attempt it was yellow and I also noticed in the bottom right hand corner that the voltage display had also turned green - it was grey the first time. I think this was the culprit that for whatever reason, the software may have not been seeing the good voltage I was sending and this somehow prevented the software from working it properly.

The second thing I noticed was that there was information that I missed on the first go-round. The software gave a prompt saying that this would take longer than usual as a firmware update would be required. Don't remember seeing that the first time either? This could explain why it was taking so long as when I started the process again, it took every bit of 45 minutes for the software to complete. It then asked me if I wanted to update another file which I forgot what it was but when I said yes, it prompted me saying that I had to make sure I had the most current purge valve? Crap, now I need to pull the wheel off and the liner and dig out the purge valve to check it? I said screw it and hit the yes key anyway. Since my dash was still flaunting a Transmission Fault at me, I knew It couldn't get any worse.

So in total it took about 45 minutes for each routine to run and at the end of loading that file, it did a DTC clear on the TCM and voila, the fault disappeared on the dash. Man, that was a good feeling. So I anticipate that I didn't brick the TCM but I honestly haven't driven the car yet either. It may present something as I start moving it but I will know by days end either way. The odd thing is that there is still a TCM update that it wants me to do and I am inclined to just go for it now that I have already seen the worst. If the end result becomes a bricked TCM, I will have learned plenty but I tell you what, if you do not have anything wrong with your transmission and want to simply reset the adaptive, take it somewhere with someone who has experience and let them do it. I may or may not have dodged a bullet here and if not, I am ok with it since I am having transmission issues bad enough that I may have to replace it anyway.

So there you have it.
Off to send an email to ZF to see if I can get to the bottom of the displayed results. Hoping that it becomes a valve body issus so I don't have to swap out the transmission completely.

 

Can you post the codes?

Did you mess with the connector sleeve during your fluid change? Did you disconnect the wiring harness? It can be put in too forcefully and push the pins in. The collar also has to be rotated the right way and leave a predefined gap with the transmission body. I suppose a lousy connection there would likely throw all kinds of codes. A leak at the sleeve can also flood the connection internally and throw codes.

Before messing with the valve body, have you done research on the bridge seal (another cheap but hard/scary to reach seal), and the accompanying tube seals? They are all behind the valve body, so accessible from under the car.

There are cheaper solenoid kits out there, too. Entire valve bodies are more pricey. There is also the Sonnax ZIP kit...

 

I personally didn't mess with anything but that's not to say that someone prior to me didn't?
All I did was drain the fluid, replace the filter and fill up the fluid again. I have heard about the electrical connections and also the bridge seals. That will be my next step to check. Once I drop the pan again I will dig into it deeper and hopefully get to the root of this problem. I do have that 2nd to 1st lurch though and most believe that this is indicative of valve body aging issues.

My plan at the moment is to wait to hear from ZF. Hopefully they can tell by some of the data I presented where exactly to trace down this problem. Funny how I spoke to 2 different shops and they both said, you need a new transmission, before knowing anything about what's going on? One of the shops are my buddies and they are kinda tongue in cheek sorta dudes. They said yeah, you need to go for it and tear into that puppy.lol.

I will follow up with every scrap of information I can get my hands on.
BTW - I did get the car out for a run and no issues were presented. I can't say it's working any better yet because I have to give the car a good drive to get the adaptions setup. I could do the routine in the software but finding a place to follow the instructions perfectly is damn near impossible in Las Vegas. I also don't want to put any time on the tranny if there is an issue that could potentially be stressing out internals.

 

Holy moly; that was a nail-biter! This is giving me courage to have my '05 XK8 transmission flashed somewhere, ( the local dealer won't do it, they insist on nothing less than a $7,800 replacement). Can't wait to receive the next episode....!

 

Well is wouldn't have any problem doing it now.
I've gotten through the nail biting process lol.

If your transmission is really acting up, you can swing it by and we can run some tests with the software. We will record together on camera the risks associated with the other stuff if you want me to do them lol. I wouldn't do anything to your car that I haven't already done to mine.

 

Anything for science! I'll send you a PM and let's talk tomorrow or the next day...

 

Here are the transmission related DTC's that I had pulled from before

General and Performance Codes
P1260 security input
P1571 brake switch malfunction (fixed)
P1582
P0171 system too lean bank 1
P0174 system too lean bank 2
P0191 fuel rail pressure sensor circuit range / performance
P0430 catalyst system efficiency below threshold bank 2

Transmission codes
P0729 gear 6 incorrect ratio
P0733 gear 3 incorrect ratio
P0735 gear 5 incorrect ratio
P0730 incorrect gear ratio
P0720 speed sensor circuit malfunction

 

Just a thought but could those engine related codes have been upsetting the transmission and once cured and cleared resolve your issues?
I know you have some possibly strange current readings in the transmission but those could be normal for an old transmission?

 

Another thought - if there's an issue with one of the speed sensors, then the TCM can't calculate the correct gear ratios, hence the other trans. codes?

 

You should definitely fix these before doing anything else with the transmission. Have you checked your fuel pressure reading over OBDII? Should be a solid 55psi, with only a few tens variation. Seems like your sensor may have to be replaced, or at least thoroughly checked. It is at the end of the fuel rail, passenger side. A 10 min job, 2 screws and about $50. This might explain why it is running lean, and throwing a restricted performance. Also, check the fuel trims, you might be pegged at +25%. These lean burns are not good, lead to high temp and possibly destroy catalytic converters. You need to bring those in the low single digits. Start at idle.

Best of luck, keep us posted.

 

My issues are far from over lol

 

Funny you should mention that because I also did a road test to monitor the O2 sensors and fuel pressure! I shot a video of that as well but I distinctly remember seeing the pressures running from low 50's to mid 60's. If what you are saying is accurate about pressure deviation, we have found another culprit

 

One of the videos was shot to clearly monitor the wheel speed sensors and as you can see, they are all operating normally and in harmony

 

But there is also a speed sensor on the transmission, something like output shaft speed sensor. I am not sure which one is trusted first for the gear selection. If yours is defective, or the harness is damaged, it might explain the codes...

 

P0720 is nothing to do with the ABS sensors, which will throw Cxxxx codes when there's a problem.

Trans. output shaft speed sensor circuit:

 

Hey Guys,

So Redline dropped by today and I was able to catch a bunch of measurements off of his car as well. He has a 2005 example.

So far I have not been able to find any gross difference between the two cars measurements.

Both vehicles run fuel pressure on the rail at between 55 and 67 PSI. The tenths variation tolerance isn't stacking up in this case unless you mean at idle? As soon as the car is under acceleration, the fuel pressure does vary between these two values.

I also noticed a similar condition with his pressure sensors in the tranny. Similar high values displayed in the same gears? I missed the ZF techs phone calls twice today but tomorrow I hope to have an answer on that.

I will continue to work on the emissions issues and see what I can figure out. Sadly, the 2003 MY is the worst performing on the JLR-SDD software. I reset adaptions on Redlines car and it took less that two minutes AND a status bar is displayed as it worked. It took my TCM nearly 45 minutes and I had no status bar displayed.

I had already measured the input and output speed on the car and did the same with Redlines car today. Both sets of values seem to coincide but I need to review the two more closely. Here is a video of the performance of both as well as the fluid temp.

Also discovered that my 1996 XJ6 can't be read by the software. It says it can on the British Diagnostics website but I keep getting errors on the XJ. It doesn't launch the SDD software but instead opens the WDS version based on my VIN entry. Maybe I am missing something but for now no love on the XJ

 

With great gratitude and thanks to razorboy's impressive engineering skill, my '05 XK8 shifts like new again. I had an apparently-rare but pretty consistent 1st-to-2nd "clunk" that would not go away, and the local Jag dealer refused to try to clear it up. He was able to diagnose and resolve a huge record of adaptions and a long history of old stored faults, made a couple of adjustments, and the 1-2 clunk instantly dissolved into butter-smooth shifts up-and-down. I'm going to do my best to keep it under 2,000 rpm for a little while to see what transpires, and we'll check codes again after a couple of weeks. In the right hands, the Jaguar software is nothing short of amazing for it's comprehensive diagnostics and system adjustment abilities. I grew up rebuilding engines, carburetors, clutches, and brakes, but I have to admit I feel like a dinosaur after watching him work magic with just his laptop and an umbilical cord to the OBDII connector. Nothing like getting a few bugs worked out to restore the pride and appreciation of owning this fine-but-finicky touring machine. Thanks again to razorboy for his excellent detailed posts and selfless willingness to help a fellow motorist out. And then again, that's what this forum is all about!

 

Engine faults commonly upset the trans (*). I would not bother to work on the trans until the engine is running properly under all conditions - including fuel trims within sane ranges.

(*) not least because engine+trans co-operate via network messages and those do not account for faults

 

Are you making a real measurement with an actual gauge? If so, it measures pressure relative to atmospheric pressure and will definitely fluctuate. The sensor at the rail measures fuel pressure relative to manifold pressure (this is why there is a vacuum line to it). This should be a lot more stable. That value is available over OBDII, as a standard PID.

I did a run this morning on my way to work. With TorquePRO/ELM327, it measured a pretty solid 55psi, but had a technical min of 48psi, and a max of 56psi. These extreme values are recorded, but cannot be seen with the naked eye. At idle, and under acceleration, the number looks like 55psi.

 

So I am still working on this and I am cautiously optimistic on most fronts.

A lot of the DTC info I collected I believe was residual from when I bought the car and it had a cracked EGR tube. I loaded new DTC's the other day and there is nothing in there now in the way of performance issues of any critical nature.

I used the software as I described to reset the adaptions and it also forced me to do a firmware update to the TCM. I had no choice in the matter.

I have been driving the car the last couple of days and I have to say, the majority of the issues have completely disappeared. Even the 2nd to 1st bump is now pretty much non-existent. Again, I am saying this cautiously because the car has a habit of coming back after me once I say I feel something is finally resolved.

If I had to say something to close this thread right at this moment, I would say that a transmission fluid change on a higher mileage car should almost definitely be accompanied by a TCM adaptive reset. Not only my car but also the other XK8 that I reset have seen massive improvements after doing this. My ongoing theory is that if you don't know when the fluid was ever changed (if ever), there is a very good chance that the oil level is low and also very contaminated. Because the TCM adapts to conditions and driving style, it is my theory that the transmission also adapts to the bad and/or low fluid levels. Once this has been corrected, the adaptions that are stored are working against the new fluid and this would take many many miles of crap shifting and issues until the TCM finally gets it all sorted out.

Currently after two days of driving the car, the shifts have all improved dramatically and up to this point, I have seen no errors on the dash or DTC's stored on the transmission. Now on the ECM side - there is a little way to go.