Last summer the car had the "Cruise Control Not Available, Check Rear Brake Lights"...and turned on the yellow warning light. Have nothing at this time; trans shop told me this was one of the codes....he told me the others, but I did not write them down but did say the TCM needs to be reprogrammed, which of course they are unable to do.


The brake lights and cruise control work fine.


I am thinking the TCM is failing when cold and locks/unlocks the torque converter until really warmed-up and then all seems fine.


I have contacted Dan at JagBits again to keep checking on the availability of the new TCM/valve body and am also going to ask the dealership about attempting the TCM reprogramming without the replacement part. Have also been searching for a used transmission.


Anyone want to buy a 2006 XK8 convertible with less than 59,000 miles........

 

Lanny, I'm no expert, but you are all over the place with this. Those codes could have given me and all the really really good guys on this forum a little more direction. Give them a call this morning and see if they have them.
Nice car and hate you are having so much trouble. The right guy could solve this, just got to find him/her.
You are not the first to get a run around from people trying to find issues with a XK8.
Don't give up on such a great car.


Wayne

 

Lenny,

You are all over the place with this transmission issue and I can understand you desire to get it fixed but the bottom line is that it all points to the transmission. The trans shop that pulled the additional codes did they give them to you? If not can you call and see if they documented them. I am surprised that when Jaguar pulled the codes the last time when they told you the TCM needed to be replaced they did not see the other codes or did they not tell you about it or did it just come up.

If you need information or cost of a TCM/Valvebody call Eriksson and see what information they can provide for you. I am attaching a link for them.

Link Eriksson Industries

It is my opinion that you are spending a lot of energy, time and possible money for another cause for your problem. Lenny step back and relook your problem over and move forward.

 

Lanny, Just a thought regarding your transmission problem, particularly the temperature related surging. I had a similar problem to yours, the surging noticeable when cold fading noticeably at normal temperature, when consulting with my excellent local Jaguar specialist he recommended having the mechatronic unit(TCM) software updated.
He went on to explain that Jaguar deliberately put the surging in the software to enable the gearbox to generate heat from cold and so get the car to normal temperature as quickly as possible for emission purposes.(He has some authority in these matters due to working in Jaguar's Technical Department for a number of years previously).
Unfortunately I only found out about this after another garage ruined my mechatronic memory when downloading this software update incorrectly and I had to have another gearbox fitted by my specialist.

 

From what I can remember Jaguar said they could not reprogram the the TCM because of a problem with it.

 

Gus, After the botched download from the first garage I took it to caused the TCM to be corrupted, the Jaguar specialist could not overcome this and download the latest software so recommended a second hand box would more cost effective option than buying a new mechatronic unit.

 

That link I provided will get him to a reconditioned valbebody with TCM

 

Everyone, sorry that I seem to be "all over the place" with this issue, I am relating what the shops have told me.


Here are the facts:
1. The surging IS temp related. I did not think so at first as I had not driven the car long enough to find out that the surging does stop after 30 - 45 minutes of driving. This is the wife's car and her daily commute is only about 20 minutes and she tells me it surges all the way to work. It was not until I drove it one weekend that I found out that once warm, no more surging.


2. The dealership tech says replace the TCM/valve body. He also said that he would first attempt to reprogram the TCM however there are cases where the reprogramming fails and then the trans will no longer shift out of 1st gear. So the dealership wants to have the new TCM/valve body on-hand before they attempt the reprogramming. The dealership never gave me any codes.


3.The shop that told me there were no codes in the transmission and that the U joints needed to be replaced was just wrong. Will never been seen in that shop again.


4. The trans shop got four codes (I will call them today to see if I can get them). One of the codes was the brake switches, however there is no yellow or red warning light on the dash or message in the display. I did have the "Cruise Control Not Available, Check Brake Lights" message last year or so which is when I removed the brake switch assembly, cleaned switch contacts and re-soldered the connections. This removed the above warning and have not had any warning messages of any kind.


If I can get the codes from the trans shop today I will post them. I may try to get a newer OBD II scanner and get them myself as well. If I get them I will post them.




I think the dealership tech is correct in that the TCM has a fault. I have talked to them again and they are willing to attempt to re-program without a new TCM/valve body in-hand, although I have found a new one is available ($2830) and I will contact Eriksson Industries to see what they have.




Hopefully this lengthly post clears-up everything.

 

Okay, the trans shop gave me the following codes:
1571: brake switch
P0480: cooling fan control
1774: no idea
1799: CAN TCM/ABS circuit malfunction


I tried using my code reading this morning and got only P1111....so I think my code reader is not capable of reading the Jag codes; need to get a newer reader.


I do not understand if 1571 is true, then why has the warning light not come on? As I stated above the cruise and brake lights work fine.


Now the 1799 is intersting, but I have no further info on it.


The 1774 is just a question, either I heard trans shop incorrectly, or their code reader is wacky.


TCM re-programming is scheduled for Feb 2; going to wait until thoes results are in.

 

Use this list for your codes.

Link http://jagrepair.com/DTCforms/X103_P_DTC_OBDII_R1.pdf

Two of your codes are for the TCM issue

 

Your reader is probably fine and indeed it IS reporting a Jag code (P1111).

So, you can be fairly sure you have no other codes.

But.... this is for the PCM (aka ECM). Ordinary tools only report for the PCM.

It looks to me like the shop tool was also reporting only the PCM.

It is entirely possible there were some old codes stored - maybe false ones due to a low power condition.

 

GUS...thank you for the proper list of codes. I had gone internet searching but was not finding the correct information....now I have it.


Thanks again.

 

From the OBDII Book:

• P1571: Brake ON / OFF switch; brake cancel switch malfunction (Brake ON / OFF switch – normally open; brake cancel switch – normally closed)
• P0480: Radiator cooling fan module drive circuit malfunction
• P1774: CAN TCM / Linear Switch Module network malfunction
• P1799: CAN TCM / DSCCM network malfunction

From the 6HP26 diagnostic book:
Causes:

Pins:

If you look here: Jaguar 2003 Electrical Guide

You can see that GB2 is the connector of the TCM, location: "TRANSMISSION CONTROL VALVE ASSEMBLY".

Now that we have the data, it is looking increasing likely to be a problem with the TCM. Seems like the CAN part of the module is somehow off-line.

I would put one more last ditch effort into a cheap thing: In order to get to the TCM, the signals have to go through the plug on the side of the trans. I would check one last time that this plug is A-OK, especially that none of the pins on the trans side are pushed in, creating an open circuit. Pictures here: http://www.thectsc.com/images/pdf/6_...eplacement.pdf.

Past that, it is probably time to call around and see if the TCM alone can be fixed, or if the entire valve body/tcm has to be swapped.

 

More reading...

http://www.superv8.co.uk/wp-content/...ting-Guide.pdf

ZF & JLR obviously are aware of these issues.

If you go for a reflash, note this:
„THE GOLDEN 6HP26 RULE":BEFORE FLASHING A TRANSMISSIONTHE TRANSMISSION ADAPTIONS MUST BE RESET WITHOUT EXCEPTION

 

Very interesting reading....thank you.


When I take care into Jag dealership on Feb 2, I will ask to talk with the tech (Tom) that will be performing the TCM re-programming and ask him about the "golden rule" above.


I am going to ask if I can be in the service area with Tom.....doubt it, but worth a try.

 

Here is the latest:
Took to Jag dealership for the TCM reprogramming, service advisor was quite uneasy about doing this and repeatly asked..."are you sure you want to do this??"


Went ahead and tech (Tom) cleared the adaptives and then was able to reprogram the TCM without any hitches, glitches or anything else....100% sucessfull!!!!!


Wife drove home...and says no difference....still does the surging / TC unlocking/locking oscillation as before.


Have two choices at this point: live with it or remove TCM/valve body and either replace them or repair the TCM.

 

From the limited amount of material I have read on this topic, I would suggest that it's the Valve Body (possibly cracked or broken) needing a rebuild or replacement; the Torque Converter needing a rebuild; or the transmission fluid (possibly it has been replaced and you are unsure what type/make of fluid is installed in it).
Since it generally happens when cold it is possible the fluid has not warmed up enough to get through a possible blockage in the filter or elsewhere (oil cooler) and thus prevents full TC lock-up.


The general issue seems to be fluid pressure loss thus the surging when not at operating temps.


Recommend new (remanufactured) valve body from ZF, or have it rebuilt by revmax.com or buy a SONNAX zip kit or you should consider entire valve body (mechatronic) swap or rebuilt.


A new filter and Mercon SP fluid may be the best solution.


It is your car so it's entirely up to you on the best way to proceed now.