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VW Touareg 2004 issue with TMC

I have a 2004 VW Touareg that I bought 4 years ago. I bought it with check engine light on after getting advice that there is no a major problem with it, I took it to VW dealership to run a diagnostic test and they told me that there is no problem with the car. However, the car could not pass the annual smog check. It simply get rejected. I took it to a couple of non dealership shops and they told me the problem with car is the TCM, Transmission Control Module or code P0864. The car runs great and never gave me any problem at all. None of the shops told me the solutions except to take it to the dealership and have the TMC refreshed. As I said, the VW dealership told me that there is no problem with the transmission. Any idea what to do with it? I want to sell the car and please help.

The dealer says no problem, then why can they not get the CEL off? The car cannot pass emissions unless the light is off. You may need to go over their heads and talk to a regional representative. A phone number should be in the owner’s manual and online.

Inde shops may not be able to help you on this b/c it probably requires the VW scan tool to turn the light off. Also, despite what they told you, there may in fact be a problem in the transmission that will have to be fixed before the light will go off. They may have meant that the problem just won’t likely cause you a drivability problem, but there’s still something wrong. As mentioned above, the emissions folks will probably insist the light be off before they will even test the car. Don’t try to work around this either, by disconnecting the battery, pulling the light bulb, etc, b/c it won’t work. Your car’s computer will tattle on you when you take it in for emssions testing.

Actually, the check engine light is directly related to the transmission. The gear display PRNDL is all highlighted whenever the CEL is on. Occasionally, the PRNDL indicator lights clears and shows only the specific gear engaged either P or D, and the CEL also disappears as well on its own. That happens about three to four times a year. I also discovered by accident that when I park the car on a steep spot where the gear is tightly engaged, then the CEL and PRNDL light also clears and I take it straight for smog check and have the test conducted while the engine is on. And it passes. Once I turn off the engine, the CEL comes back and PRNDL indicator gets highlighted again. I have done that four times in the past four years since I acquired this Touareg. That’s why the independent auto shops I visited advised me to have the TCM, transmission control module refreshed at the dealership because it might be receiving a faulty signal from the computer. My concern is that the dealership already told me that there is nothing wrong with the transmission. And that’s why I am here seeking advice from others who probably know what the dealership don’t.

You don’t say where you live but you may have a nearby state without inspections where you can sell the car.

Has anyone bothered to simply check the wiring for the TCM? It sounds like the CEL is intermittent - ? If it has been at the dealership with the CEL on and the code present then they are full of it. Or perhaps one could say - fine, there’s nothing wrong with the transmission. But the TCM is throwing a code so there is something wrong with the transmission control system.

Anyway, any shop should be able to inspect the wiring harness and plugs and grounds and such to look for issues. It might be that you would need a dealer to evaluate and otherwise deal with the TCM itself. (Computer capabilities issue). In that case, you need to find a dealership that will take it seriously. If they say nothing is wrong, what is their explanation for the error code?

Transmission code or not, btw, it is connected to emissions issues. If the trans isn’t working properly it won’t be running as efficiently as designed and thus producing more pollution than by design. That’s what the whole OBD II system is built around.