Where Is Odometer Mileage Stored?

Odometer information is stored on a small EEPROM chip on the circuit board. The chip can be read and written to using a serial programmer. The information is coded in HEX characters.

Is mileage stored in ECU?

In many cars, the ECU stores the mileage. In other cases, the body control module (BCM) stores the information. In some newer vehicles, you may not need to do anything. The mileage will automatically show up on the new instrument cluster when you install it.

Does the PCM store the mileage?

PCM stores the mileage as well as most of the other modules do. If you swap out the original PCM it'll throw a code but wont trigger the CEL saying that the PCM was replaced with a non original one. By swapping the original back in it'll clear the flag. If a dealer cared, they can easily tell if its been swapped out.