As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STL-LAS - FLT NR 940 - NR 2 BUS OFF LIGHT AT GATE WITH APU RUNNING AND BAD ELECTRICAL SMELL IN FLIGHT DECK. STANDBY POWER OFF LIGHT ILLUMINATED ON GROUND. REMOVED AND REPLACED APU GENERATOR PER R6D49005. OPS CHECK GOOD. REFERENCE AWXA960041.