Rain Bird MV FAULT

I have a Rain Bird esp-lxi16+. I keep getting an MV FAULT error. Can thi be fixed? The manual says i have an electrical fault has ocurred in the master valve or pump start relay circuit. How do I diagnose and fix that? Please

There is a terminal on your timer labeled MV OR Pump Start. It is for just that, to open a main valve, or energize a pump start relay...in conjunction with opening a zone valve. If you have something connected there, it is telling you there is a fault...short,whatever. If nothing is connected to that terminal...the timer is kapooey!