My tach has been broken for a while. Everything else is running fine. Any suggestions on where to start to try and fix it?

Thank you.

99 accord ex 4 cylinder

 

Earlier cars, the tach signal comes from the ignitor (in the distributor), but starting 1998 it comes from the PCM. So if the PCM isn't getting the proper signal from the engine sensors, it'll throw a CEL for those sensors. Are you getting a CEL?

If not, then you have to run down wiring issues between the PCM and the cluster. After ruling out bad wiring, I guess you're left with a bad tach.