As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT LT ON AFTER LANDING. RAN QRH AND APU FAULT LT ON AGAIN AFTER SECOND ATTEMPT. GROUNDED - YES. FOUND FAULT CODE 49-41011. ACCOMPLISHED B737-800 FIM 49-40 TASK 802. FOUND FOULED IGNITOR PLUG. REMOVED AND REPLACED IGNITOR PLUG AND LEAD PER B737-800 AMM 49-41-51 AND 49-41-52. APU OPS CHECKS NORMAL. NO FAULTS.