Hi,
This is the instructions for my 2001 325i. They should be the same for your car.
To reset the indicator:
- The car should be off
- Put the key in the ignition
- Hold down the left instrument button (the trip odometer reset)
- While holding the button, turn the ignition to position 1 (radio)
- You will see a test menu
- Keep holding the button
- After several seconds, the word "reset" will appear
- Let go of the button and press again
- The indicator is reset!