90 caddy with speedometer/odometer problems

Hello. I have a 90 model cadillac sedan deville and the speedometer, odometer and the fuel range mileage device is not working it is an engine code 3. It has the digital gauge read out. what is the best way to fix it or go about trouble shooting

I don’t have any data to look at this for you unfortunately. I would check to see if the areas you mention have a common power supply point. There may be a bad power connection to them. If you haven’t already, check all the fuses in the dash and under the hood for a problem there also.