This is a follow-on to my throttle body/TPS thread as the problem turned-out to be the transmission control module. So.....took car to dealership and was told the TCM needs to be replaced; cost about $4500....OUCH! I was told that they would first attempt to flash the TCM but this could make the car undriveable; took car home and did alot of reading. After about a week decided to make an appointment to take car in and try flashing the TCM and if that did not work then replaced TCM. Dealership tells me that they need to get new TCM in house before attempting flash, made sense. HOWEVER I was then told that a TCM is not available and no ETA as to when one would be!!
Soooo now I am really stuck.....called JabBits and same results...not available, no ETA.
CRAP!
Now I am thinking about trying to find a used transmission...but how to I know which 6HPxx trans it is?

 

Did you call ASI to see if they could repair it?

Gus
www.jagrepair.com

 

I expect 6HP26 and should not be hard to get used TCM or whole trans - it's used on many cars.

I would NOT use any Jag dealer. They treat trans as sealed lump, mysterious innards. You want a trans shop or possibly a jag indy who's clued up.

BTW if this is the engine surge issue then it may be the TC not locking up - fairly common on S-Types with 6HP26. People routinely live with it for years. TCM is not to blame. Fix is replace TC and again a trans shop is the best place, not the dealer (unless they employ one of the great techs on this site).

 

I bought a spare matching #TCM for my 4.0 and it's a drop in, but it's more likely the ECU/TCU would have to reflashed if you get a used one. There are indy shops that can do this.

 

I had this same surging problem in my 05 VDP. Replacing torque converter solved the problem. Worth considering before you start spending big bucks.

 

Gus: No I have not called ASI yet as I thought I should have the transmission model before doing so.


I completely agree about the dealership.....will be taking car to another shop.


Also note that the TCM is attached to the valve body in this transmission and not next to the ECM/ECU like in the 4.0 engines.


If it were the torque converter...would there not be fluid leaking....so I would have some drips or other signs on the undercarriage?

 

Read my posts about the rebuild on my transmission on my '69 XK8. If you need a transmission, get a used one!!!

 

larueb: I assume you mean your '99 XK8...not '69 right?


I found your posts on your rebuild trans.....


One other question: is continuing to drive the car damaging the transmission? The dealership said no, but then they may just want to replace the transmission at $11,000 plus labor!!!!!!

 

The leaking is internal to the torque converter. There is a seal that goes bad that prevents proper fluid pressure from being applied to the lockup clutch. Somewhere along the way ZF changed the seal design to improve reliability and a rebuilt TC would have the revised design.

Usually the symptom is slight surging at neutral throttle, maybe 50 or 100rpm. Sometimes there is a vibration that is sort of like going across a rumble strip. It also tends to be worse when the trans is cold. If the problem gets bad enough you may get a code for the torque converter lockup clutch.

My has done this for >20k miles. It goes away when everything is warmed up so I just put up with it. I found a used transmission for cheap and figure I can rebuild it when something really goes wrong.

One final question... How many miles and have you ever changed the trans fluid and filter?

Jaguar claims some sealed for life nonsense but ZF recommends 60k intervals.

 

Jaguar don't claim that it's sealed for life or any such and haven't for at least 6 years (which is when I read their TOPIX where they clearly state to change fluid etc).

I can well imagine some dealers don't read the tech data or ignore it but hey BMW, M-B etc dealers all have some ignorant staff too.

 

Got under the XK8 this morning; found the TCM connector...it was at the rear of the trans. Disconnected and all contacts looked fine, sprayed with some electrical contact cleaner and remated.


Also found the numbers plate...yes it is a 6HP26.


Also pulled the left rear wheel off to check the reluctor ring....and once again the 2006 is different from the previous years. The ring is internal to the rear hub. I removed the ABS sensor and checked the ring anyways and it was fine.


Have really only noticed the surging when at a light throttle, cruising 40 - 55 mph....have not taken onto highway to see if surging occurs at other speeds....also changing position of right foot ever so slightly and surging will stop until at a steady-state position again...level road.


So I do not think it is the TC.


Also, yes the trans fluid / filter have been changed. Mileage on the car is 58,100 miles.


And finally....seems the 2006 has more in common with the 2007 than the earlier model year in terms of components and where "things" are located.


Still going to be calling another shop and see what they have to say.


Thanks everyone.

 

For a reference point and something to look at there are some on ebay $620-2700

http://www.ebay.com/sch/i.html?_odkw...ssion&_sacat=0

 

None of that diagnosis tells me anything that clears the TC as a suspect.

 

Yes, sorry. '99 is correct.

 

Good work. Eliminated easy possibilities.

I remember reading on this board that the issue with the torque converter was for the early 6HP26 (2003 model year), and that the better parts were fitted to the later cars. Your '06 would presumably have the latest parts. Also, for what it is worth, checking in JTIS does not reveal an updated part number for the torque converter, so not sure how to continue on this thread.

Also, can you re-state the diagnostic with the codes? You listed P1797, which indicates an error condition in the path between the ECM and the TCM.

Check last page here:
6HP26 Diagnostic

Is this error always there? Can you clear it? Does it come back, or did it come on once and is now gone for ever? Are there any other codes? Sorry to seem to task you, I am trying to help. It feel like the priority should be to investigate and eliminate this code.

 

Have not checked codes in awhile...will do so and report back.


I had cleared the codes before taking it to the dealership last week; pulled codes today and had the same two:
P1111, P1797....so appears the P1797 is consistent.


Will be taking to a different shop on 1/6....to say what they have to say.

 

Ok, This is "good" in a sense.

If it was me, I would try and investigate the "other end" of that cable to goes to the transmission (the plug you checked under the car, on the transmission itself). Part of me thinks it might be behind the instrument cluster (I believe this is where the various buses connect to one another), but it could just as easily be on the ECM itself, I just don't know. I figured the electrical manual would help. I would try and have a hard look at any of those connectors, check for signs of leaks, corrosion, contamination, even check for animal or other signs of mechanical damage. Also take a hard look at any ground points in the area. Separately, the "bin" where the ECM is located has a drain at the bottom. It is known to plug and let the bin fill up during heavy rain. Just another "zero dollar" item to check.

If you take a second read at the 6HP26 diagnostic document I linked above, it says it is the TCM that complains of not hearing from the ECM, which possibly suggests that the TCM is just fine, but is somehow is not able to communicate with the ECM. Maybe the ECM connectors need attention as well.

Have you tried the "hard reset" procedure as well to fully reset all the electronics?

Best of luck. Keep us posted.

 

I have already been to the ECM and found that the electrical connector has a "special" bolt that prevents me from disconnecting it and checking the contacts. The bin is clean, drain clear, etc. Everything looked fine.


I followed the TCM harness back and could see that it goes directly to the ECM "area" and the harness looked fine...no bad spots that I could see.


I did not see the "hard reset" procedure....will go back and take another look.
Took another look and did not see any "hard reset" procedure.....where is this at?

 

The hard reset is just to disconnect the negative battery cable and touch it to the positive one for 10-15sec so as to discharge all of the electronics.

This clears codes and resets all of the ECU adaptations, although it will NOT reset the transmission adaptations. To do that, you need to use the SDD dealer software.

 

Got it....thought the "hard reset" was something other than touching the battery cables together.


Car is on its way to the "other" shop...will find out by day's end what they have to say and want to do.