As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NEW OIL PRESSURE SWITCH CAUSED ERRONEOUS LOW OIL PRESSURE ANNUNCIATION AND HOUR METER FAILURE. REPLACING THE SWITCH WITH A UNIT OF A DIFFERENT LOT NUMBER RESOLVED THE PROBLEM WITH NO DEFECTS TO EITHER THE OIL PRESSURE INDICATION AND RESTORED THE FUNCTION OF THE HOUR METER.