High input means the pressure sensor is not responding to changes in pressure that are actually occurring. It is stuck at one extreme. Low input and intermittent input are other faults that can occur. See

http://www.obdii.com/codes.html

It might be a loose connection or faulty sensor (either manifold absolute pressure or barometric pressure sensors or both are used on various cars to provide a reference against which the fuel pressure is measured).

Indeed, though, it might not come back. The effect of the error might be a loss in fuel economy or minor driveability issues (and failure of an emission test). If it comes back and stays, you will be able to trace it.