1. Turn on the car by pressing the Power button
2. On the Odometer/trip meter button on the steering wheel, press to show "Trip A" on the screen.
3. Turn the car off - push the Power Button.
4. Find the "km/h-MPH" button above the clock set buttons
5. Hold down the "km/h-MPH" button while pressing the Power button
6. Continue holding down the "km/h-MPH" button, and release the Power button.
7. The screen will say that the oil maintenance data is being reset.
8. When the reset is complete on the screen, release the "km/h-MPH" button.
there are 3 generations.try this one.if that's not the correct one,try this one below.
How to reset oil service light Toyota Prius third generation XW30 after changing the engine oil (U.S.A. only).
The oil change system should be reset. Perform the following steps:
Turn the “POWER†switch OFF with the trip meter A shown.
Turn the “POWER†switch ON with the MPH or km/h button held down.
Keep pressing the button until the odometer indicates “000000†and the multi-information display indicates that the reset is complete.