OK, where to begin. First thing first. You may have a controller that has some "issues". There have been some instances throughout the US with this exact problem and there is either no MV hooked to the controller (master valve or pump start relay) and it shows this error, or there is a legitimate problem with your master valve. First, look to see if you have a wire, or wires, hooked to the MV circuit. If so, disconnect it and restart the controller. If the problem goes away, you have a bad solenoid, or pump start relay .If you do not have a wire, or wires, hooked to the MV circuit, you will need to take the WHOLE controller down (not just the faceplate) and swap it for a newer one (no worries it's under warranty) preferably with one that has a date code of around mid July or later.
Josh
Irrigation /Landscape Lighting / Pump and Well Specialist