Hi guys long time no post!

Im trying to get my 850 R through another mot but it failed because the ABS light is on. It has been on since i disconnected the battery to do some work a while back and it just stayed on since. The ABS & TRACS lights are on all the time but there is also a problem with the speedo as it seems to have an intermittent fault - problem is i can be doing 80mph and the speedo sticks on 30mph for about 30 seconds then all of a sudden it will shoot up to the correct speed, this happens most days. I have done a bit of research and apparently it could be the board on the pump but i want to be certain before taking it off and wanted to know if the speedo indicates a different fault?

Can anybody enlighten me?