Is it possible to change the odometer reading on a car engine

odometer tool

Some Owner question is :”Is it possible to change the odometer reading on a car engine? If not, what mechanisms are in place to prevent that from happening? “

Many odometer engineer reply:

Karl Walter:Turned wrench for a few decades.

“My knowledge ends at about 2004, so new cars may have more safeguards.

You can only lower the odometer reading on a mechanical odometer, and it usually requires taking it apart, because there is a often a ratchet inside that prevents simply driving it in reverse.  You can increase the reading on a digital odometer by providing a pulse, but it only up counts, the pulses have no direction.

You can try to over run the mileage eeprom register, and it might result in zeroing the mileage and counting up  again.  If display reads 999,999 maximum, then you can run the pulses at  the maximum the speedometer can detect them,.  I tested one from a late 80’s gm car and it was around 600mph, so it would take over a month, and then who knows?  You might end up with an odometer that says 999,999 and goes no further.  You also might exceed the eeprom writes, and end up with who knows what number.  Imagine it’s a lease car, and you owe $.25/mile on 900,000 miles.  You will have to sell your house.

Anyway, it’s all illegal, unless you are replacing the odometer and you are matching the actual mileage, so don’t do it. Plus, mileage is recorded when regestering, dealer service, and smog checks, so it’s easy to get caught. –Karl”

Vlad Borsan “My car likes to break, and I like to fix it”

 “Of course it’s possible.

Used car “dealers” in Europe do it all the time. And no matter how advanced the technology behind it is, there is always a way to trick it.

For example the newer cars have the odometer reading written at the same time in both the card and the electronic key.

The best way to tell the age and mileage of the car is to look on the actual car (not the odometer). My car for example now says ~250000km, but the body and transmission are way older (maybe 400-500K km), while the engine is definitely newer (was changed + does not yet have all the problems that a similar engine of higher mileage would have).”