Reg. CME Error

We are getting frequent +CME ERROR: 3. What are the possible causes for the error and how to recify the error. Also, how to avoid such errors?

S. Vanee

I’m sorry I can’t answer your question because I’m just new in all this.

But if you could answer to me a question I would be very grateful.

unused inputs where must be tied? Ground or I can leave them No Connected?