As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU WILL NOT START FAULT LIGHT ON. ACCOMPLISHED APU BITE TEST. FOUND FAULT CODES: 49 31175 49 52192 49 31160 49 31168 & 49 52188. REPLACED APU FUEL CONTROL UNIT REF MM 49 31 11 000 801 / 49 31 11 400 80. PERFORMED FUEL CONTROL UNIT INSTALLATION TEST NO DEFECTS NOTED. PERFORMED APU BITE PROCEDURE NO CURRENT MAINT MESSAGES.