Fiat Punto Mileage correction over OBD-II

[kido resuri]

Hi,

I'm trying to do mileage correction on my Fiat Punto mk2b (year 2004).
I'm using ELM327, and managed to connect to the Dashboard unit, and I'm able to change the mileage, but only more than the original.

This is what I have so far:

Initializing ELM327 and setting connection/display paramters

ATZ
ATCAF0
ATCFC0
ATCRA7C3
ATSH7B0
ATAT1
ATST29

Connecting to dashboard unit

85021081

Keeping connection alive, need to send every second or so, or else the dashboard disconnects

85013E1

Reading odometer

850221211

Dashboard response, odometer value:

F1 05 61 21 02 D7 43 00

In this case, odometer value is 02D743, that is 186179 km

Set odometer value, in this case to 02D744, 186180 km

85053B2102D744

Dashboard response, if mileage is higher than original value:

F1 02 7B 21 00 00 00 00

Dashboard response, if mileage is lower than original value:

F1 03 7F 3B 12 00 00 00

Anyone knows the command to set a lower mileage or reset to 0?

[kido resuri]

Forgot to mention, I'm able to zero out the mileage by writing the eeprom, but I'm trying to learn how to do that through the OBD port.
Any hint would be appriciated!

[steveleo]

Does ELM support huge messages? As you can set mileage to 0 by OBD but that needs some big command (more than 50 bytes in total).

[kido resuri]

I guess I could try if I knew the command.

[kido resuri]

Since then I found out that AlfaOBD can reset/write whatever mileage I want, with ELM327, so it is indeed possible with an ELM327 interface.
If I have time and interest, I might be able to capture the packets, but I'll need a man-in-the-middle for a wifi ELM327 adapter.