As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUT ATC WAS UNABLE TO RECEIVE TRANSPONDER . AC RETURNED TO THE GATE (BTB) AND MTX GROUNDED AC . MTX PERFORMED A SYSTEM TEST OF THE TCAS SYSTEM AND ATC WAS ABLE TO PICK UP THE IDENT, IAW B 767 AMM 34-45-00. NO FURTHER DEFECTS NOTETED . MTX RETURNED AC TO SERVICE .