As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GE DIAGNOSTICS REPORTS NR 1 ENGINE TREND DATA SHOWS A SHIFT IN EGT HOT DAY MARGIN ALL OTHER PARAMETERS NORMAL. EGT INDICATION ERRORS ARE SUSPECT. GROUNDED-YES. REMOVED & REPLACED NR 1 ENGINE CJ10 HARNESS, REF B737-800 AMM 73-21-06 INSTALLATION TEST PASSED.