As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT MESSAGE WITH ATTEMPTED APU START ACCOMPANIED BY REPORTED UNUSUAL ODOR BY FLIGHT ATTENDANTS IN THE BACK OF AIRCRAFT. APU INSPECTED AND BURN SMELL COMING FROM APU STARTER. R/R APU STARTER MOTOR PER MD90 AMM 49-44. INSPECTED APU STARTER CABLES/WIRE AS REQUESTED. R/R RELAY R2-792 AS PRECAUTION. REPLACED BATTERIES. (LP# 4688972, 4688973, 4688980)