As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUT, AFT CABIN TEMP, FWD CABIN TEMP EICAS MESSAGE APPEARED, A/C RETURNED TO GATE (BTB) AND MXT GROUNDED A/C. PERFORMED T/S IAW FIM 21-61 FT 804. NO FAULTS OR DISCREPANCIES FOUND. MTX DEFERRED IAW MEL ABX-21-61-1-2 AND RETURNED A/C TO SERVICE.