As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT NUMBER 454, DURING TAXI PREPARING TO DEPART RSW THE APU HAD AN AUTO SHUTDOWN (FAULT LIGHT ILLUMINATED AND EICAS MESSAGE APU FAULT DISPLAYED). AIRCRAFT RETURNED TO THE GATE. MAINTENANCE REMOVED AND REPLACED THE APU CONTROL UNIT (ECU) IN ACCORDANCE WITH AMM 49-61-05, FUNCTIONAL CHECKS GOOD AND AIRCRAFT WAS RETURNED TO SERVICE.