My response is simply an educated guess. I have never done this specifically for this problem, nor do I know of anyone doing it. That said, you can remove the gauge cluster and look for severed solder joints on the ciruit board. This solves problems with many other digital displays in the car (radio, climate control unit, etc.) Seven-segment displays are usually dirven by chips designed specifically for that purpose. Perhaps one of the input or enable lines to the chip has come lose. You will need a solder gun with a fine tip and thin solder as well. Search here or use google for instructions to remove the instrument panel. Good luck.