As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT DURING PREFLIGHT CHECKS FINDING THE TCAS SYSTEM FAILED. THE SYSTEM WOULD NOT EVEN TEST. THE TCAS SYSTEM FAULT WAS DEFERRED ON MEL 34-45-01-00A. DURING THE MAINTENANCE EVENT, THE MAINTENANCE TEAM REMOVED AND REPLACED THE TCAS PROCESSOR. OPS CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.