As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TWO APU START ATTEMPTS BOTH RESULTED IN FAULT LIGHT , NO START. ACFT GROUNDED. R & R, AND TESTED APU IGNITION UNIT IAW MM 49-41-31-400-801. TEST PASSED. APU BITE SHOWS NO CURRENT FAULTS THROUGH 3 START CYCLES. REPAIR CONFIRMATION SUCCESSFUL IAW FIM 49-40-00-810-805.