As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, OIL FILTER BYPASS CAUTION LIGHT LEFT ENG CAME ON IN CLIMBOUT. REDUCED THRUST - LIGHT WENT OUT WHEN THRUST REDUCED TO IDLE. INSPECTED CHIP DETECTORS, NO DEBRIS FOUND. INSPECTED AND REPLACED BOTH THE MAIN AND SCAVANGE OIL FILTERS PER M/M, ALL ITEMS LEAK CHECK OK. NO MESSAGE RETURNED ON ENGINE RUN. FWD TO MEL 79-00-02.