As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ELECTRICAL BURNING SMELL IN COCKPIT & FRONT CABIN DOOR. ODOR REPORTED IN GATE. SMELL ONLY ISOLATED TO LT TRIM AIR SYS, REGARDLESS OF AIR SOURCE. ENG RUN ACCOMPLISHED BY CREW & NO ODORS WHEN LT MASTER TRIM AIR IS SELECTED OFF. ENG RUN CHECKS ACCOMPLISHED IAW AMM05-51-50 WITH LT TRIM OFF, ODORS DISSIPATED IN COCKPIT. CABIN ALSO CLEAR.