As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUT ALL THREE A/C TEMP CONTROLLERS INDICATED INOP, A/C RETURNED TO THE GATE (BTB) AND MTX GROUNDED A/C . AFTER TROUBLE SHOOTING FOUND APU CONTROL UNIT BAD, REPLACED APU CONTROL UNIT IAW AMM 49-61-05. OPS CHECK GOOD, A/C REMAINS NO ETOPS . A/C IS RETURNED TO SERVICE .