As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GRI - THE CREW ELECTED AN AIR TURNBACK AFTER NOTING THAT THE LEFT OIL PRESSURE GAUGE FLUCTUATED BETWEEN 60-90 PSI IN CRUISE. AN UNEVENTFUL LANDING WAS ACCOMPLISHED. MAINTENANCE SOLDERED BROKEN WIRES ON A CANNON PLUG AT THE PRESSURE TRANSDUCER. SYSTEM WAS OPS CHECKED SATISFACTORILY.