Can I reprogram a TCM to work in my car? The TCM in my 2003 A8 is faulty. It works only when the car is hot. It stays in LIMP Mode and I have to turn it off and on quite a few times too get it out of limp mode when the car is warm. The number on the TCM is 4D0 927 156 EL. I have a 4D0 927 156 CP. I got it from a 2000 A8. I plugged it up and the car runs great but on the display cluster it shows PRND4321 intstead of the PRNDS...
Will a VAG-COM be able to reprogram and reset the TCM.. I am desperate!! I cant find the correct TCM except from the dealer, and you guys know the cost!!

 

2003's are D2's in the U.S. instead of D3's More importantly, it is a different (5 speed) tranny instead of the D3's 6 speed, and I sure bet the control boxes are different.

BUT, I own a 2000 A6 4.2 with the same basic tranny and motor as the D2. I can't tell you about the TCU interchange at the part suffix level exactly. BUT...if it works it works!

Meanwhile, I think I know your display answer. First, presumably you know if it goes into the backlit mode then it is in the SAFE mode and the tranny stays in 4th gear and car just barely gets moving. Presumably that is not the case with the newer TCU box. So assuming it's normal, the box that shows the "S" at the end of the display relative to the "54321" at the end of the display hasn't been reprogrammed to what is referred to on the D2 board (or C5 board) as "Sport mode." Apologies if I have that reversed by the way in terms of which display sport mode shows.

Net if my theory is right, someone changed either your car or the donor car to program the box for "sport mode." It is indeed done with VAG COM. Search the D2 or C5 board for something like TCU and Sport or maybe better TCU and 00032 (the value put in via VAG COM to C5's (don't recall if the same on D2's; might be 00022 or something). Very easy to do in any case. Sport mode basically alters the adaptive learning in the TCU. It shifts out of first a little later and downshifts a little quicker. May affect the TIP (manual shift) function too, but it's been too long to remember that. Search the old posts. Both modes work fine by the way from experience, so if you don't have access to a VAG COM you can just leave it be. Also, this is strictly a "user hack" as far as I know, so dealers wouldn't even be officially familiar with it. Way back when, someone with a D2 stumbled on it and posted to the board years ago now.

And no, for the D3'ers, I have never heard of a similar tranny shift mod for the D3/C6. But owning both, the D3 already has much more responsive tranny controls than the preceding generation.