As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU WILL NOT START AND HAS FAULT LIGHT COME ON DURING START SEQUENCE. GROUNDED-YES. ATTEMPTED TO START APU FOLLOWING STEPS ON B737-800 FIM 49-40 TASK 802. FOUND NO NOISE FROM IGNITER PLUG. REPLACED IGNITER PLUG LEAD, REF B737-800 AMM 49-41-52-400-801 AND IGNITION UNIT, REF AMM 49-41-31-400-801. APU OPERATION NORMAL.