Is chip tuning detectable via OBD check?

Hello,

In the engine control unit (ECU), specifically module 26, a checksum is being generated for my Polo.
It does not change when adapted. This master data block consists of only one field.

Could this already be a form of data provision that could be used in the future to identify modified vehicles, for example, during police checks, simply by reading this measurement value (if the normal value for the respective engine control unit version is known)?

Hi Ulf,

If this is indeed a checksum, then it should also change during regular software updates from the dealer. Knowing our district supervisors as I do, their equipment is likely outdated, making it impossible to determine whether the system contains the original software.
Furthermore, I don't believe that the system calculates a new checksum every time it starts and stores it in the aforementioned memory location. First, it would take too long, and second, VAG would definitely use it to exclude tuned engines from the warranty.

And even with chip tuning, it might be possible to correct the checksum to match. And by that, I don't just mean adjusting the checksum to match the data set, but rather leaving the checksum at its original value.

While it currently requires a significant effort, if what you're saying is true, then there would soon be corresponding plugins for the characteristic curve editing programs.

Just to understand: You would then increase the values that are important to you (which, simply put, would make the checksum larger) and, in return, decrease the values of "unimportant" fields (which, simply put, would make the checksum smaller again). Therefore, it might be possible to maintain the original checksum even with modifications.

Regards,
Guste.

guste100 wrote:

Just to understand: You would then increase the values that are important to you (the checksum would - simply put - become larger) and, in return, decrease the values of "unimportant" fields (the checksum would - simply put - become smaller again). Therefore, it might be possible to maintain the original checksum even with modifications.

So far, so good.

If the checksum, for example, were only calculated from the most important characteristic values of the injection quantity (soot, engine speed, driver request), it would become more difficult to implement compensations .

ulf wrote:

However, if the checksum were, for example, only calculated from the most important characteristic fields of the injection quantity (soot, engine speed, driver request),

it would become more difficult to implement compensations .
Okay. However, my knowledge isn't sufficient for that. I only know the area that is protected by a checksum. Everything in that area is secured (including "unimportant" data). Theoretically, you are right, and the checksum could consist of multiple individual checksums, one of which might only check the tuning-relevant data fields. However, I don't think people thought that far ahead back then.

But: shhh . Let's not talk about it anymore, otherwise they might use our discussion later as a basis to do exactly that .

Regards,
Guste.

Hi, who says that the corresponding function must also display the correct checksum?
If you're already modifying the STG (presumably a software configuration file), you just need to figure out where the value is being read and simply return a "everything's okay" value. Do you have to patch some code in addition to the identifier fields?
It shouldn't really be a problem. However, with current ECUs, it is relatively difficult to read program code and data from the outside.

Best regards, Rainer.