Newegg

Post tune shifting on the Cayenne has not received rave reviews. There was a guy on one of the touareg forums that put a new Transmission Control Unit (TCU) in his rig, had the new tune done, then put the original TCU back in and was able to preserve the original shifting. Does anyone know where this TCU is located? A new TCU is about 650 bucks and I am sure it needs to be coded to the car by the dealership.

​​​​​​https://www.pelicanparts.com/More_Info2/95861812040.htm

deilenberger

The TCU is located under the front passenger's seat. It isn't clear to me what you're attempting to achieve here. Do you mean that the TCU programming is changed by the "tune"? Shift points changed? Can you refer me to a link outlining what the complaint actually is? (Post tune shifting)?

One thought that comes to me - if the tune changes the HP/torque curves enough the old shift points may not be optimal. There is a simple fix for that - reset the transmission adaptations and let it learn where it should shift with the new torque/HP provided by the new tune. It would eventually learn that anyway since it is adaptive - but you can hurry it's learning curve along by doing an adaptation reset (doable with an iCarScan, dunno on Durametric - but probably, and I'm certain PIWIS does ie.)

Newegg

Thanks for the info on the location. Yes I am referring to the way the car shifts after the emissions fix. There is a very long thread on this in the emission fix thread.
You do make a good point about the engine tune and the tranny tune being matched. Certainly could screw things up if I installed the old tcu with the old mapping/tune settings.
May have to set the whole idea to the side for a while and see how this all plays out.

Eskimo1

One Touareg guy bought a used TCU and installed it prior to bringing his car in for the fix, and then swapped it back out post-fix, and said nothing about having to change a thing (programming, etc.) while swapping, and has even offered to loan out the used one for folks getting their fix performed. Wish I had thought of that!

There is talk of JRAuto (the Canadian Tuner) being able to do transmission tuning soon (was only posted a week ago), but several noted that Aisin transmission tuning has been attempted many times before with no success at cracking their encryption.

deilenberger

It's still not really clear to me what this swap "avoids" or prevents. If there is an issue with adaptation - just reset it and let the system learn it over again.

As far as an Aisin transmission - the 958 doesn't use one. It's an 8 speed ZF (German).. perhaps the Touareg is an older model?

Eskimo1

The transmission programming was changed as part of the emissions fix. It's the hard-coded "mapping" that controls the shifting behavior, not adaptation.

The diesel does not use a ZF trans. It uses an Aisin TR-80SD, same as the Q7/Touareg.

chsu74

This I have noticed. Wonder how much an ECU tune can overcome this?

deilenberger

That's the very first mention of diesel in this thread. Shows why listing the year/model of the car being discussed in either the thread title, or the first posting, or the poster's sig, or all of these - is a damn good idea.

Eskimo1

True - always good to specify, but when Touareg is mentioned along with "emissions fix", pretty safe to assume he's talking about the diesel.

deilenberger

This is what I replied to:

While Touareg is mentioned - "tune" is mentioned but nothing about emissions fix.. so..

Newegg

JRoach

eskimo1, does the hard coding you mention apply to all CD MY’s? There is a discussion about how to reset the TCU’s learned behavior.

cwheeler

It applies to CD that have had the factory emission "fix." This has been discussed in-depth for several years now. The shift behavior post-fix is..... less than ideal, and I would argue, as would most others that care, it shifts in a detrimental manner for the sake of emissions. And trying to teach my wife to shift properly, as it's her daily (and NOT a car person) is near impossible. She cares more about the steering wheel heat than paying attention to the car. Not that there's anything wrong with that

Having the TCU tuned is on my list of things that must get done...

Cw