View Full Version : 2.8 ECM incompatible with S4 tiptronic TCM -- Please Help me!

05-13-2012, 08:57 AM
Hi! I recently installed an S4 tiptronic transmission in my A4 2.8L I didnt tought I would have so much problem making it working right!

First, I tried it with my A4 TCM ans it didnt worked so I bought an S4 TCM (8D0 927 156 DL) and installed it.

Now my transmission can communicate with the TCM but my Engine Control Module is now incompatible with the TCM.

What I get in VAG-COM is :

18263 - Powertrain Data bus software version monitoring P1855 - 35 - 00 --
18249 - Engine Control Module / Transmission Control Module Incompatible P1841 - 35 - 00 --

I also realised that the software coding of the A4 TCM is 00000 ans the S4 TCM is 00002 Ive tryed to recode to 00000 but when I click Do it! nothing happen and it stay on 00002.

The car is currently running in LIMP MODE (stuck in second gear) and kicks hard between Neutral Second(drive) and reverse gear.

In Vag-Com I can see an other difference between the two TCM. the shop number of the A4 is WCS 00000 // and the S4 is WCS 07461

As far as I know, the TCM is what I need to recode to make it accepted by my ECM. But if that doesnt work is there any way to recode my ECM to make it accept my S4 TCM?

All I need is an ECM that run my stock 2.8 block but accept my S4 TCM so I can get out of LIMP MODE

Any suggestion? If there is no way to make it work is swapping a 2.7 my only option?



When I try to Recode with VagCom does I need to Login first? I dont have my Owner Mannual... What is my Login Code? I need to use A4 Login Code or S4 Login Code as I am working on an S4 TCM.. ??

thanks again!

05-13-2012, 02:30 PM
Why did you swap in an automatic? I'm more concerned about that.

05-13-2012, 03:00 PM
Because my Base car Is Automatic. And I tought I would be cheaper to get the same thing and not having to change anything else... At this time I wasnt thinking of Electronic compatibility problem because machanically the A4 and S4 share the same Auto transmission.

05-13-2012, 04:37 PM
Not exactly, the S4 gearbox has different gear ratios than the A4.

05-13-2012, 05:15 PM
The ratios in the automatic are the same.

take a look :

My a4 is 2.8q tiptronic

05-13-2012, 07:00 PM
I really think you'll have better luck with A4 TCU. I mean, who is to know what the ECU and TCU are talking about? The S4 TCU probably wants to talk about boost. Your A4 TCU has nothing to say about that. Hence they are "incompatible". I don't think this is just a coding problem, they just aren't going to talk. You didn't mention any specifics at all as to the behavior with the A4 TCU...

The Audiworld links you provide are rife with wrong information. However, from a quick look at my Bentley, it does appear that the 2.8 and 2.7 Tiptronic ratios are the same. It also shows that they never share the same torque converter. The S4 always showed a different converter code than the 2.8 A4. That would probably cause a code and maybe limp mode.

I think you're really into uncharted territory here with swapping up the tiptronic boxes. Generally speaking in the auto repair world, you ALWAYS MATCH THE CODE on the trans. If it doesn't match, you find one that does. With all this electronic controlled transmissions, you can't just swap stuff around unless you really know what you are doing. Else you wind up exactly where you are...limp mode central. And nobody wants to be there.

Good Luck.

05-13-2012, 11:04 PM
I already tryed with A4 TCU but the problem is between the transmission and the TCU... if i put the S4 TCU my problem is between ECU and TCU...

I hope I can make it work because my budget is limited and I cant afford putting this tranny out. getting a new one and starting over... at this price i'll part-out the car and go buy an S4...

05-14-2012, 05:20 AM
I'm pretty sure your S4 TCU > A4 ECU problems will not be rectifiable. Please explain the exact issues you had with A4 TCU. Again: You didn't mention any specifics at all as to the behavior with the A4 TCU...