As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU DET INOP LIGHT ILLUMINATED UPON PUSHBACK. GROUNDED - YES. VERIFIED DISCREP - HARD FAIL. ENG/APU FIRE DET MODULE BITE PER B737-800 FIM 26-10 TASK 802 SHOWS APU TAILPIPE DET AT FAULT. RANG OUT SAME DETECTOR AND READ 160K OHMS - SHOULD BE 4K OHMS. REMOVED/REPLACED TAILPIPE OVHT DET ASSY REF B737-800 AMM 26-15-01. OPS NML REF AMM 26-15-00. GROUND VERIFICATION TEST GOOD.