8404 buzzer

[oilrodJ]

After doing all my hydraulic fluid change oil change front axle gear oil change got on to crank it had buzzer going off under dash. No lights lit up on dash? check battery it was ok.
Never had anything like this before when Battery wire got loose? Any ideas?

 

[oilrodJ]

I am not a mechanic not that familiar with Tractors this tractor I bought used had very low hours been a great tractor so for.