As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU MX BLUE LIGHT ON AND OIL LEVEL FOUND LOW. ACFT GROUNDED. COMPLETED ALL STEPS OF TSR IAW FIM 49-95-801, AND FIM 49-90 / 813, PARA (B) (F). FOUND EVIDENCE OF AN OIL COOLER LEAK. REMOVED AND REPLACED THE OIL COOLER IAW AMM 49-91-41. LEAK CHECKED GOOD.