As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE SITTING AT GATE C15 IN DTW THE APU PERFORMED AN AUTO SHUTDOWN. THE FLIGHT CREW SMELLED SMOKE AND SAW IT COMING FROM THE GASPERS. THE PASSENGERS WERE EVACUATED AND CFR RESPONDED. NO FIRE OR HOT SPOTS WERE FOUND. MAINTENANCE FOUND THAT THE APU ENCLOSURE WAS SOAKED IN OIL. FURTHER INVESTAGATION FOUND A RUPTURED OIL LINE ON THE APU. THE ENCLOSURE WAS CLEANED, THE APU DEFERRED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.