As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT LIGHT ILLUMINATED DURING APU START. GROUNDED - YES. PERFORMED APU SHUTOFF VALVE OPERATIONAL TEST FOUND VALVE TO BE FAULTING REF B737-800 AMM 28-25-02-710-801. REQUIRES REPLACEMENT. REMOVED AND REPLACED APU FUEL SHUTOFF VALVE ACTR AS REQUIRED REF AMM 28-25-02-400-801. ACCOMPLISHED APU FUEL SHUTOFF VALVE ACT OPS CK OPS CKD GOOD REF AMM 28-25-02-710-801. STARTED APU OPS CKD NORMAL. ACCOMPLISHED APU BITE CK NO FAULTS FOUND REF FIM TASK 49-60 TASK801.