As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ETOPS PDC OIL LEVEL CHECK, APU OIL LEVEL DISAPPEARED AND MAINT. LIGHT CAME ON. GROUNDED - YES. PERFORMED B737-9 FIM TASK FOR MSG 49-94304. OIL LEVEL SENSOR FAILURE. AFTER INITIAL EVALUATION TEST, ALL INDICATIONS RETURNED TO NORMAL. MAINT LIGHT EXTINGUISHED-NO ACTIVE FAULTS SHOWING ON STATUS, INTERMITTENT FAULT. APU STARTED AND OPERATED NORMAL OK FOR SERVICE. FIM TASK 49-90-00-810-811.