Rancher shift/speedo problems

Hello all,

I have a 2000 Honda Rancher 350 ES that has been having some problems that I need to fix. What happens is that it will start and shift but after a little the shifter stops working and I have no speed at all, just says 0.

The shift motor works, replaced an ECU that was newish from a foreman I had laying around and all fuses are good and new. Just replaced the wire harness because the fuse box on the old one was crappy and the same issue was kind of there. It was working yesterday for a little and went to move it today and nothing.

When shifting though if it stops when riding I can shut it off then turn it back on and the shifting comes back until it stops again.

Need help please and any info would be appreciated!