Speedo / Ecm problems

2008 700×2 problems started with hot lite showing on a cold start up,unplugged battery neg machine ran fine ,2 days later back in the bush when machine idles but as you add throttle it completely dies,check out manual it says unplug speedo test drive machine runs but no speedo no reverse 4×4,let bike sit plug speedo back in ride for about 50 -100 yards low & high icons flashing back and forth on speedo,engine wants to die when throttling up , unplug speedo engine seems to work fine,
Ps there’s been condensation inside the sealed speedo could this be the problem or is it the Eco,both are exspensive want to buy correct item for repair

Mike