The ECMM gives you a number 4
(Error Code MM board).

Maybe the MM board (control board) is loosely connected to the hash boards?
Or maybe the MM board is damaged?

Do you have another MM board to try?

You can find the log text description guide here https://canaan.io/wp-content/uploads/2020/03/log-Description.pdf
Other Canaan documents: https://canaan.io/service/447

When ECMM

• , it means that the MM board is in normal state. When ECMM [1], it means that the MM board may have problems, or it may have poor contact with the hash board. The specific problem of the hash board can be judged by the value returned below. When Echu displays 0 or 512, it means normal. If Echu displays 513, it means abnormal.