My beloved 2008 XF 2.7 sometimes goes into what i will describe like a gear slip. When accelerating between 50 to 55mph moving up, the rpm will suddenly jump from say from1600/1700 to 3000 and Gear Fault displays on the dash. The car immediately loses power or acceleration from that moment until i stop the car and clear the Gear Fault with a scanner and only then will i be able to drive the car normally again until it happens again. Or sometimes when i try to accelerate fast, like move from say 40/45 to 60/65 in seconds.

I must say this hardly happen when am driving within Nottingham but definitely when on a fair distant trip. The fault code it always comes up with before clearing is P0814, any idea what this problem is and how can it be resolved

Thank you

David

 

Hello, David!
My guess is that you are using some generic OBD reader, which do not gives you full code, because this specific code is not mentioned in workshop manual. However, the manual provides two possible options:
1. P0814-01 Transmission Range Display Circuit - General Electrical Failure. The possible cause for that PRNDS LED failure. The proposed action in the manual is: Suspect transmission shift module, check operation of PRNDS display, check and install new transmission shift module as required, refer to the new module/component installation note at the top of the DTC Index.
2. P081462 Reverse Output Circuit The possible cause for that is the transmission range display circuit. Action: suspect the TCM, check and install a new TCM as required, refer to the new module/component installation note at the top of the DTC Index. So this is what the manual provides for your case - so, most likely there is no mechanical fault, just electrical. And my blind guess is that it is more likely it is the second fault, because I doubt that the transmission shift module related fault appears on the dashboard - at least it did not appeared for me, when I had that usual problem with stuck gear selector, and also, if the first option was the cause of the problem, you would also notice that the LED display which is located next to your gear selector.

Hope this helps somehow and good luck!

 

Your are right on the scan tool i used. Bought one on ebay sellers claimed is for Rover and Jaguar.

Thank you for your thoughtful response, i will take it to the garage and get back on my experience

David

 

Hello Gunars
​​​​​​ I could not find any garage with the Jaguar Diagnostic tool but paid in a garage for the attached diagnosis.

I was told to replace the Transmission Control Module based on the outcome.

As a "Saturday mechanic" I was wondering if anyone knows the location of the TCM on 2008 Jaguar 2.7d so as to determine if I am able to set a weekend aside and replace it.

David

 

Hello, David,
The manual says following: "The TCM is an integral part of the Mechatronic valve block which is located at the bottom of the transmission, within the
fluid pan. (...) A fluid pan is attached to the lower face of the main case and is secured with bolts. The fluid pan is sealed to the main
case with a gasket. Removal of the fluid pan allows access to the Mechatronic valve block."

With kind regards,
Gunars

 

Gunars

Thanks so much,

When you say the fluid pan is attached to the lower face of the main case with a gasket. Is this the same as that which is replaced during transmission fluid change?

 

Hello, David! Yes it is the same fluid pan, which is replaced during transmission oil change (see picture, TCM is component Number 3, pan is Number 5).

Additional few important things, according to the manual: 1) during replacement procedure it is very important to protect TCM from any electrostatic shock 2) during replacement you will encounter several oil seals, need to be replaced.
With kind regards,
Gunars

 

You are God's sent.
Since the diagnosis points to the TCM as the culprit, what advise or suggestion would you give me.

I have searched online for a new TCM or a working used but cant find any.

Can the one in my car be repaired or how do i get past this. Love the car, its the family's priced car, only done 79,000 mile.

Your advise is highly appreciated.

David

 

Hello, David, thank you for your kind words! Unfortunately I have no practical experience with repair of the gearbox , I have been lucky from this point of view, however, in my specific situation I would also consider an option to change the whole gearbox, which might make sense, because they are easily available and are quite cheap ( (which makes sense, because they seem to be quite sturdy). Meanwhile it seems that used TCM module are sold only together with valve body, and cost the same as the whole gearbox.

I can see that on ebay there is even one gearbox for only 205 £ in UK currently available, and it even provides 30 day warranty, I think that is a quite reasonable deal. I do not know typical labour costs in your country, but from my experience in my country - it might be much costlier to actually open up the gearbox and tinker with the valve unit and module, than to change it as a whole, because, most of repair shops better avoid touching insides of the automatic transmission, but changing the whole unit is not so complicated. Also, it is important to note that after opening the oil pan it is mandatory to change the oil and the pan/filter, however, if you find a reliable used gearbox with low mileage, you may consider postponing change of fluid for later, because oficially, the gearbox is filled "for life", and, while it is a good idea to change transmission fluid after some 100 000 km, it is not something that needs to be done immediately.

In the manual I could not find any information or remark, whether TCM needs to be re-flashed or re-programmed, if it is installed on another car, but just to be better safe than sorry, I would also make sure that mechanic, who changes the gearbox, is able to to tinker with this programming part as well.

Reprogramming or initialising of the TCM is not a difficult procedure, if you acquire appropriate cable and Jaguar/Land Rover diagnostic software. I bought the cable and the software online from China, and it works well enough. I must admit that once I accidentally bricked several modules, including TCM, because the portable PC run out of power (well,, if one tinkerswith diagnostic and programming, stable power suplly for both car and the PC is essential), but, luckily, it took some 20 minutes only to upload all the right software back.

Good luck!

 

Hi David
Judging by what you have posted so far. I would recommend that you take your automobile to a good transmission shop.