As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU WOULD NOT START ON TAXI IN, LOW OIL PRESSURE LIGHT ILLUMINATED. GROUNDED - YES. COULD NOT DUPLICATE ISSUE. APU STARTED UP EVERY TIME, DID THREE STARTS WITHOUT ENGINE AND JUST FOR PRECAUTION REMOVED AND REPLACED APU OIL FILTER OPS CHECK GOOD NO DEFECTS NOTED. REF B737-900 AMM 49-91-12-400-802. RUN BOTH ENGINES OFF APU AND TURNED OFF THE APU, AND STARTED APU WHILE BOTH ENGINES RUNNING. NO ISSUE FOUND.