After reading the error memory, the mileage suddenly increased

Hello,

I hope I've posted my topic in the correct section.

I purchased a VAG-COM device a few weeks ago, and today I tried out the OBD function for non-VAG vehicles.

More specifically, I read the error memory of my Smart ForTwo. It's a gasoline-powered car from March 2005.
In the evening, when I arrived home, I wanted to write down the mileage in my logbook as usual, but suddenly, instead of approximately 19,500 km, the odometer showed over 22,000 km.

I've been searching the internet for several hours now, but I haven't found anything on this topic.

I simply read the error memory (no errors found) and then clicked on "clear error memory."

While this sudden difference isn't tragic for me personally, it might be a problem for the tax office. I also wonder if there might have been some tampering with the car (I bought it used in August).

Can anyone help me, or has anyone else heard of similar phenomena?

So, if you use your mileage log as proof for the tax office, then this situation is extremely problematic. I would even go so far as to say that this could lead to the mileage log not being accepted for the entire year.

Best regards, D.

Hi,

Quote:

Can someone help me, or has anyone heard of similar phenomena before?

It is 100% certain that the VAG-COM device is not responsible for the odometer reading being changed, either intentionally or unintentionally.

For all those who repeatedly ask me: You can only change the mileage of NEW odometers (with < 100km) using VAG-COM!

Regarding the issue: either the software/hardware in the Smart's control unit is faulty, or reading the data triggered some kind of internal function that synchronized the displayed value to the 'correct' value... but these are just my personal speculations, as I don't know much about Smart cars, and there are certainly many people who know more about this than I do.

If I were a software developer for smart control units, I could definitely imagine implementing such minor "pranks" like the trigger function mentioned. It's probably fun when a tester is connected during the inspection (AU) and then the odometer reading "jumps" .

Best regards, Rainer.

Basically, Rainer has already said everything important, but here's a little more for clarification. When reading the error memory via OBD-2/EOBD, a read-only access is performed on the control unit. Even if you wanted to, it's not possible to change the mileage via OBD-2/EOBD because that would exceed the scope of the protocol. While clearing the error memory involves a write operation, it only sends a command to the control unit and doesn't directly write anything. From our perspective, there are only two possibilities: either you are mistaken and the mileage has not changed, or there is a software error in the control units of your Smart.

We have not encountered a similar phenomenon before, and there are some customers who frequently use VC (presumably a type of cleaning agent or process) on Smart cars in the workshop.

Thank you for your answers; I had already suspected (that I would be a special case again ).

I never thought that a VAG-COM device could be the cause of the problem.

I'm going to try posting it again in a Smart forum, because, to be honest, I don't really want to deal with a Smart dealer. I don't have much hope of getting a better answer there than I'm getting here.

As I said, any error on my part is definitely ruled out due to the daily record-keeping (unless I somehow went on a trip to southern France in a trance and forgot about it).

Since there are no other apparent issues with the electronics (or at least, there seem to be none), I'll just leave it as is for now and see what happens during the next diagnostic scan...

@D.:
Thankfully, the recording period is finally over (it only covered the three months for...).
Proof of business use (no mileage log required), so that I won't have any issues with the tax authorities.