on board computer

Can you disable or reset the on board computer that keeps log on the mileage and hours.

As I understand it, there is a small lithium battery in the ECU that won't allow that. If you disconnect your battery, the ECU is allowed to re-set the performance information (sensors, etc.) to troubleshoot potential problems, but I hear that there is no way to re-set the mileage/hours on a unit. Again, as I understand it, it was mandated by federal law a few years ago to keep fraud down in the re-sale market. You can always replace the ECU with a used one, but that's at your discretion.