# ECU swap...



## '05JettaSPE (Jul 10, 2008)

Alright guys, this is a fun one...
I have a 2006 Manual Transmission Rabbit, I had been toying with the idea of getting tuned and found an ECU with the C2 93 octane street tune on it for sale that came out of a 2007 Automatic Rabbit. I ordered the ECU and went to the dealership today to have them swapped so they could do the immo defeat. ECU is now installed and I love the tune, so much better. Of course, there are issues with the mismatched ECUs that are going to bug me.

Issue 1)
I'm throwing a CEL due to communication issues with the transmission controller, obviously since I am the transmission controller, no big deal, just an annoying light.

Issue 2)
I'm throwing a traction control light, again with communication issues, meaning I have no traction control. This is kind of a big deal to me since I live somewhere that gets snow.

So, I am going to start investigating these things, see if I can figure anything out and whatever I do find I will document on here in case someone else encounters it.


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## thygreyt (Jun 7, 2009)

by the looks of it, the ECU you installed was for an automatic.

those are/were the codes i had after the tranny swap.


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## '05JettaSPE (Jul 10, 2008)

How did you overcome them? Or did you just get a different ECU?


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## thygreyt (Jun 7, 2009)

there is no easy/practical way to do so.

best i simply sell/remove the ECU


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## DerekH (Sep 4, 2010)

Can you not vag com to tell the ecu that its in a manual car now?


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## thygreyt (Jun 7, 2009)

you can, on the getaway module and abs.


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## '05JettaSPE (Jul 10, 2008)

I figured I probably could, I think I'm definitely going to run into issue with the traction control, and anyone with an 06 rabbit and a vag com go into their traction control module and dump the hex from it? I have a feeling it is just going to be telling my ECU which traction control module it needs to talk to now


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## DerekH (Sep 4, 2010)

At least the car works though, i sure would like it if i didn't have to press the button to turn the traction control off every time i started the car.

I would guess that everything is fixable with vag com, i have no idea where you should start though.


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## thygreyt (Jun 7, 2009)

DerekH said:


> I would guess that everything is fixable with vag com, i have no idea where you should start though.


nope, it isnt fixable on vag com. You'd need a tuner to do it.

The dealership has the tools, but they wouldnt do it for me.

in my case, unitronic took care of it. According to them, it wasnt easy.

and yes, i did try on vag com.


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## '05JettaSPE (Jul 10, 2008)

I'm going to go home and plug in the vagcom tonight, I have a couple ideas, the CEL for the transmission communication thing is no big deal, it doesn't hurt my feelings any, but I want my traction control back and I think I can get it if I figure out what to put in the long coding for that module.


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## thygreyt (Jun 7, 2009)

'05JettaSPE said:


> I'm going to go home and plug in the vagcom tonight, I have a couple ideas, the CEL for the transmission communication thing is no big deal, it doesn't hurt my feelings any, but I want my traction control back and I think I can get it if I figure out what to put in the long coding for that module.


ok. Nothing should change, and it wouldnt work...

but do try and let us know.

maybe, just maybe your ECU wont crash and you will be able to fix it.


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## '05JettaSPE (Jul 10, 2008)

thygreyt said:


> ok. Nothing should change, and it wouldnt work...
> 
> but do try and let us know.
> 
> maybe, just maybe your ECU wont crash and you will be able to fix it.


My thought process is that between 2006 and 2007, changes were made in the EPC system of the vehicle at a component level. My 2007 ECU is trying to reach out to talk to the absent 2007 EPC components. If true, it is likely that the ECU is backward compatible with the 2006 EPC components. Again, if true, all I have to do is figure out how to tell the ECU to talk to those older EPC components. I know, my logic hinges on two theories that could be way off track.

I'm doing a bunch of research in the Bentley manual about the EPC system, and the theory they give on how it works aligns with my thought process. So we shall see...


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## thygreyt (Jun 7, 2009)

'05JettaSPE said:


> Issue 1)
> I'm throwing a CEL due to communication issues with the transmission controller, obviously since I am the transmission controller, no big deal, just an annoying light.
> 
> Issue 2)
> I'm throwing a traction control light, again with communication issues, meaning I have no traction control. This is kind of a big deal to me since I live somewhere that gets snow.


Issue 1) Manuals DONT have a tranny control. The actual Name is TCM (transmission control module) and in the automatics, this is what determines when to change and more.

If you remove it, there will be a communication error. The ECU thinks that there is no tranny.

Issue 2) Since there is no tranny (according to the ECU) the car cant determine the traction control.

The abs module Could be affected as well.

Again, i learned this because of my Transmission Swap, from Automatic to Manual. 

this is what my dash looked like









To put it simply: your ECU thinks the car is an automatic.


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## '05JettaSPE (Jul 10, 2008)

Yep, I understand that.

I like how you took a picture of your cluster doing 80 MPH :laugh:


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## DerekH (Sep 4, 2010)

'05JettaSPE said:


> Yep, I understand that.
> 
> I like how you took a picture of your cluster doing 80 MPH :laugh:


He didn't say it was his, he just said that is what it looked like. Big difference 

Also, thanks for the info Greyt.


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## itskohler (Jan 7, 2011)

DerekH said:


> At least the car works though, i sure would like it if i didn't have to press the button to turn the traction control off every time i started the car.
> 
> I would guess that everything is fixable with vag com, i have no idea where you should start though.


You should wire the switch to also turn on your engine, and put the switch on a small delay. 2 birds one stone


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## thygreyt (Jun 7, 2009)

DerekH said:


> He didn't say it was his, he just said that is what it looked like. Big difference
> 
> Also, thanks for the info Greyt.


lol. no worries, but i did say its mine.

i took the pic (last year) for a couple of reasons:

-to show the rpm at 80mph on the 6spd
-to show the dash lights.

that pic was taken 2 hrs after i got my car back from the shop,from the tranny swap.


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## '05JettaSPE (Jul 10, 2008)

thygreyt said:


> -to show the rpm at 80mph on the 6spd


I assume 2.0T? If you swapped to a 6spd on a 2.5, I would love details


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## thygreyt (Jun 7, 2009)

'05JettaSPE said:


> I assume 2.0T? If you swapped to a 6spd on a 2.5, I would love details


lol, we are on the 2.5 tech forums!  its one of the very few 6spd manual 2.5L

look at my profile:

1k-m-cbta-02q

1k= mkv
m= jetta
cbta= 2009 2.5L
02q= 6spd manual.

for the details, check on my created threads and/or my build thread. :thumbup:


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## nothing-leaves-stock (Mar 1, 2005)

fred's right. it will be tuff to have the ecu recoded and if you do i'm guessing it won't be a free or $49.99 thing!

may have been cheaper to just have gotten the c2 software for your ecu...


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## DerekH (Sep 4, 2010)

itskohler said:


> You should wire the switch to also turn on your engine, and put the switch on a small delay. 2 birds one stone


That would be pretty sweet actually.


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## thygreyt (Jun 7, 2009)

DerekH said:


> That would be pretty sweet actually.


why do you want it off all the time?


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## DerekH (Sep 4, 2010)

thygreyt said:


> why do you want it off all the time?


Because if i go to pull out in traffic and the tires get close to slipping the car decides I'm not allowed to have any power and all but stops my car in traffic. Plus any number of other reasons. If my car goes into a slide i want to be able to mash the throttle and get power instead of have it hit the brakes and make the slide worse. I feel i can control my car better without it on.


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## [email protected] (Feb 4, 2004)

I have fixed this issue before, same thing as when a manual is swapped into an auto car. 

The fix is simple with UM software. Problem is you are back at square one then cost wise. might as well just sell the auto ecu and flash the correct manual ecu from the car


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## thygreyt (Jun 7, 2009)

DerekH said:


> Because if i go to pull out in traffic and the tires get close to slipping the car decides I'm not allowed to have any power and all but stops my car in traffic. Plus any number of other reasons. If my car goes into a slide i want to be able to mash the throttle and get power instead of have it hit the brakes and make the slide worse. I feel i can control my car better without it on.


what are your mods??


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## DerekH (Sep 4, 2010)

thygreyt said:


> what are your mods??


Headerback, cai and programming. It doesn't take much to get the wheels to slip and when they do the traction controller cuts in and basically stops the car.


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