As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PRE-FLIGHT, THE AMBER MAINT LIGHT ON THE OVERHEAD PANEL WAS ILLUMINATED. GROUNDED - YES. STATUS SHOWS APU OIL FAULT, ACCOMPLISHED EXISTING FAULT CHECK REF B737-9 AMM 46-13-02, FAULT 49-89002 LOGGED ACTIVE. CHECKED APU OIL LEVEL AT THE TANK, APU OIL IS FULL. WAS ABLE TO CLEAR MAINT LIGHT FAULT 49-89002 IS STILL ACTIVE BUT MX LT EXTINGUISHED. T/S PER B737-9 IFIM TASK 49-00-00-810-817. RMVD & RPLCD APU ECU REF B737-9 AMM 49-61-12. APU OPS CHECK GOOD.