Error code 3 flashing in our odometer window on our 1992 ford Bronco fullsize 5.0 liter what is this code?

The error code is only speedo related. The vss circuit or memory which is stored in an integrated cicuit on the rear of the speedo is somehow out of calibration or the circuit is damaged. You should bring your truck to the dealer to have it reprogrammed. Their seems to be some good advice online but the problem is you only have 6 tries to get it right or the memory cache will be full and the speedo unit will need replacement. Good luck