What was found
(CAN) AT APPROX. 1500 FT, THE PILOT GOT A LOW OIL PRESSURE ANNUNCIATOR AND VERIFIED INDICATED OIL PRESSURE DROPPED TO ZERO. THE CAPTAIN REDUCED POWER TO IDLE, ENGINE INDICATIONS WERE ALL NORMAL EXCEPT OIL PRESSURE. HE ADVANCED THE POWER ONE MORE TIME AND ALL INDICATIONS RESPONDED EXCEPT OIL PRESSURE. AT THIS TIME THE PILOT SHUT DOWN THE AFFECTED ENGINE AND RETURNED TO POINT OF DEPARTURE.