As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
#1 ENGINE TREND DATA SHOWS GREATER THAN EXPECTED DATA SCATTER FOR DELTA CORE SPEED. INDICATION ERRORS ARE SUSPECT GROUNDED - YES. REMOVED AND REPLACED #1 ENGINE N2 SPEED SENSOR IAW B737-800 AMM 77-11-02-000-801-F00 AND 77-11-02-400-801-F00, ETOPS GROUND FUNCTIONAL CHECK GOOD IAW AMM 71-00-00-800-811-F00 ITEMS NUMBER 3A AND NUMBER 13. LEAK CHECK GOOD IAW AMM 71-00-00-700-801-F00 AND ENGINE RUN - EEC BITE CHECK GOOD IAW AMM 71-00-00-700-808-F00.