As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU AIR PRESSURE DOES NOT MAINTAIN PRESSURE THAT WOULD BE NEEDED TO START. GROUNDED - YES. REMOVED AND REPLACED APU WIRE HARNESS IAW B737-900 AMM 49-11-01-400-802. GROUND VERIFICATION TEST IS GOOD. NO FAULTS. DRY MOTOR MAINTAINED STEADY PRESSURE AT AROUND 29% N2 REF AMM 71-00-00. REMOVED AND REPLACED P2, T-4 AND DELTA PRESSURE SENSOR REF AMM 49-52-31, 49-52-32, 49-52-33. OPS AND LEAK CHECK GOOD.