As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ENGINE START, AFTER PUSHBACK, CREW REPORTED RT PACK AUTOFAIL AMBER CAUTION MESSAGE FOLLOWED BY AND ODOR OF SMOKE AND BURNING PLASTIC. RETURNED TO GATE. MAINTENANCE TROUBLESHOT, AND R & R RT ACM AND PERFORMED CHECKS IAW AMM. ACFT RELEASED FOR SERVICE.