As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT LIGHT GENERATOR DISCONNECT WHILE APU RUNNING AT GATE. GROUNDED - YES. REMOVED DAMAGED OIL COOLER. REPLACED OIL COOLER PER B737-900 AMM 49-41-41. APU RUNS CONTINUOUSLY WITH NO AUTO-SHUTDOWN. APU OPS AND LEAKS CHECK GOOD. NO FURTHER DEFECTS NOTED.