SCR Control Unit Replacement: Coding Required?

Hello everyone in the forum community!

I have a friend whose 2015 A4 B9 with a 2.0 TDI and SCR engine displayed the error message "AdBlue system malfunction." The diagnosis at the dealership revealed a faulty control unit, and they wanted to charge over €600 for a new one immediately...

The gentleman in question initially wanted to make sure that this was indeed the problem and did some research online. However, he concluded that it was likely the control unit (ECU), as there were a total of 8 error codes stored.

A used engine control unit (ECU) with the same part number was purchased and installed, and all previous errors disappeared. However, a new error appeared: "No communication possible with the control unit."

Unfortunately, I don't have a log file for that vehicle because it is currently unavailable. However, I hope we can still answer the question, as it seems to be of a more general nature and relates to the typical procedure when replacing an ECU (Engine Control Unit).

- Is it necessary to code/program this control unit?
- Can this be done using VCDS yourself, or do you need to go to a dealership for it? How does the process work? Is it done via a login code, or through server synchronization with the manufacturer?

Again, I apologize for not being able to provide a log file... I still hope that someone can help me with this issue.

Thank you very much!

Best regards, Alex.

Counter-question: What exactly was exchanged?

I strongly suspect that the vehicle does not have a single "SCR control unit."

My speculation is that the engine control unit (ECU) was replaced, but the immobilizer system wasn't properly adjusted. Does the engine start for a second and then automatically shut off?

Regards,
Sure.

Here is the translation of the text from German to English:

"Guste" means "gust" in English. It can also be used as a verb, meaning "to gust."

"Before/after Autoscan is missing; this would show what needs to be recoded if necessary."

guste100 wrote:

Counter question: What exactly was exchanged? I strongly suspect that the vehicle does not have a single "SCR control unit." My speculation is that the engine control unit (ECU) was replaced, but the immobilizer system was not properly adjusted. Does the engine start for a second and then automatically shut off? Regards, Guste

.

Hello Guste!

The SCR control unit was actually replaced; it's located in the rear right corner, underneath the fuel tank, and next to the pre-lift pump.

dieselschrauber wrote:

Before/after Autoscan is missing, which would show what needs to be recoded if necessary. icon_idea.gif

Hello!

Unfortunately, I missed that opportunity because the laptop's battery was already dead and the vehicle had been picked up again.

I will try to catch up on this for my own learning purposes. What exactly would one see regarding coding? And is it possible to do this independently? Is a login code fundamentally necessary for that?

Thank you very much!

Best regards, Alex.

Hi,

Just click on "Auto Scan" and read the results.
Answers many questions.

Best regards, Rainer.