As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING OPERATIONS BEFORE FLIGHT THE FLIGHT CREW REPORTED THAT THE APU SHUTDOWN DUE TO AN OIL PRESSURE ANNUNCIATOR. THE MAINTENANCE TEAM DETERMINED BY TROUBLESHOOTING THAT THE LOW OIL PRESSURE SWITCH HAD FAILED. THE MX VENDOR REPLACED THE PRESSURE SWITCH WITH A NEW UNIT. OPERATIONS CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.