i have never been able to get this to work. I hold in the trip button while looking at the LMPG and total mileage, and it never flashes!
I have managed to drag the orginal purchase mileage (42mp) up to 48, but it would be nice to have -my- mileage showing.
(it was a city car, part of a fleet.)
Make sure the car isn't running. Put it in the (II) position on the ignition. Make sure that LMPG is showing. Push and hold the trip button. It will flash after about 5 seconds of holding it. Push the trip button again and do not let go until you see "--"