As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER STARTING APU STRANGE ODOR IN FORWARD CABIN. TURNED OFF APU AND SMELL DISSIPATED. AFTER START MOMENTARY APU GEN OFF BUS MASTER CAUTION MESSAGE CLEARED AFTER ABOUT 3 SECONDS. REMOVED FROM SERVICE. APU PLACED ON MEL. MEL CLEARED BY REACTIVATING APU. OPERATED TEMPS THROUGH VARIOUS RANGES. ALL OPERATIONS WERE NORMAL. COULD NOT DUPLICATE ANY ABNORMAL ODORS. CLEARS MEL. RETURNED TO SERVICE. NO PARTS REPLACED.