The OVP is a relay with a series fuse. Other than the fuse blowing, the only thing that can consistently cause it to be 'open circuit' is if the relay coil fails, but I think you would have your ABS light on then. If the relay contacts are poor, the symptom would be problems with idle and running. You might look for sensor inputs that have failed, e.g. O2 sensor or crank sensor, causing it to default to limp mode.