As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
REF ASA T/C 78273000 CDU CHECK FOR FAULTS ENG 1 SHORT TIME FAULT 77-21131 & 77-11131, THE N2 SPEED SENSOR SIGNALS DISAGREE. GROUNDED - YES. REMOVED & REPLACED ENG.#1 N2 SPEED SENSOR PER B737-800 AMM 77-11-02. ACCOMPLISHED ENGINE RUN START IN REF AMM 71-00-00.