As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GE DIAGNOSTICS REPORTS #1 ENGINE TREND DATA SHOWS A DELTA EGT INCREASE AND EGTHDM DECREASE. EGT INDICATION ERRORS ARE SUSPECT. GROUNDED - YES. REMOVED #1 CJ9 HARNESS, REF B737-900 AMM 73-21-06-000-803. CJ9 HARNESS ON ENG #1 INSTALLED. OPERATIONAL CHECKS GOOD AND NO FAULTS ON EEC BITE TEST. EGT TEMPERATURES ARE WITHIN TOLERANCE: S1 20.87, S2 18.57, S3 18.24, AND S4 18.04.