Frequently asked questions about coding on Volkswagen, Audi, Skoda, Seat (VAG)

I am very often asked the same questions related to the coding of VAG group cars (Volkswagen, Audi, Skoda, Seat).
I will try to create a small FAQ on this topic with solutions to the most common problems.

1) “Coding and service” does not appear. What to do?
In order for the “Coding and Service” item to appear, you need to: select one of the connection profiles for Audi, Volkswagen, Skoda, Seat (which one is not important) and connect to the car.

2) How do you know if I have MQB or PQ26 or MLB-EVO?
Under the “Coding and Service” section at the top, there is a platform selection. Models are indicated there.
Older platforms are not supported yet.

3) The current state of codings is read normally, but an unknown error occurs when trying to code any option.
First, use a quality ELM327 adapter.
Second, on many cars from 2021 onwards to apply the new value, you must open the hood and activate the handbrake. Sounds funny, but it’s true.

4) In the current state of the coding, it says “Coding is not supported or faulty ELM327 device”, although other codings are applied normally. Should I change my adapter?
No. You are shown two possible reasons: either the coding is not supported, or the problem is in the adapter. If the adapter allows you to use other encodings, then it is logical to conclude that the problem is not in it. By the method of exclusion, we discard one of the reasons and we are left with one reason: the coding is simply not supported by your car.

5) I did something and now I have something wrong. What to do?
Almost all operations and the initial state of codings are stored in the encoding history. All you need is to methodically restore operations from your coding history. Moreover, this should be done chronologically from the newest to the oldest points. Until what went wrong is corrected.
The most common mistake is that people think: the problem is caused by some specific coding, but in fact it is caused by another, earlier one (let’s say they performed 10 encodings, found that something went wrong, and think on one of the latter, although the problem is real at the very beginning). Therefore, I advise: if you do not know by 100%, methodically roll back everything. Missing nothing.
I strongly recommend that you back up all blocks before making any changes. Coding and Service -> Backup.

7) What’s wrong with my adapter? It can connect and read some data, but doesn’t let me read coding state and code anything.
Once again I repeat: the quality of the adapter is important. If a bad adapter doesn’t allow you to read or encode anything, that’s good. You just need to change it. It is much worse when a bad adapter pretends to be good, but sends garbage to the car or corrupts the data read from the car. This can lead to dire consequences.

8) Sometimes saving a new value is aborted. What to do?
The communication speed with the adapter is very important. Taking into account the general “slowness” of the ELM327 adapters, as well as the many different delays that occur when transferring data along the way car -> adapter -> Bluetooth / Wi-Fi -> phone -> program (and in the opposite direction), you should try to eliminate as much as possible all factors that affect the speed of data exchange. The most common factor: Bluetooth connection to the car radio. An active Bluetooth connection to the radio can reduce the speed of data exchange with the adapter by 5 times.
Therefore, during coding, disconnect the Bluetooth connection with your radio.