Rpm gauge bouncing

[Scoot5869]

2010 t800 cm871 rpm gauge was bouncing up and down engine light would come on and leave. This was at idle truck didn’t seem be running rough but was surging I guess with the rpm’s would bounce to 300-800 range. Don’t have my computer with me to check it. I was just curious as to what may cause it ecm has 1837 hours on it with the proper files. Replaced all the fuel parts but the gear pump this spring. So far a random occurrence. Will hook up insite tonight to see what’s on it. Any ideas let me know thanks