As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER LANDING GEN #2 WOULD NOT TRANSFER TO APU GEN PLACED BOTH ENG GEN BACK ON LINE THEN SELECTED GEN #2 TO APU FIRST. BOTH GEN TRASFERED TO APU GEN. GROUNDED - YES. VERIFIED WITH APU & EXT. & ENG. RUN. REPLACED APU C803 BREAKER WITH NEW ONE. ACCOMP. INST. TEST, TEST PASS. REF. B737-9 M/M 24-21-41-400-801.