Hey. Earlier today my battery couldn’t crank the starter because the terminal was horribly corroded. I fixed that situation with terminal cleaner, a tighten, and the addition of protectant, now it’s running fine.
Except that the tripometer and speedometer are no longer working.
Yes, I checked the fuses. All fine and intact. The instrument panel lights are fine, the heat gauge is fine, and the fuel gauge is fine. Just the speedometer and tripometer do not move any longer.
Any clues?
Since your question is generic, my answer has to be generic. Most cars today get their speed and odometer data from the ECU (engine computer) which gets its reference from the vehicle speed sensor (VSS). Somewhere between the VSS, the ECU, and the instrument there is a disconnect. Your mission, should you decide to accept it, is to investigate the circuit with a multimeter and find where the discontinuity is. The State Department will disavow any connection…
To be less generic, It’s a 1999 Ford Escort. Thank you for your comment. My question is where the hell do I find that circuit??? 
(please don’t tell me i have to take apart my dashboard.)