As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT THE GATE ON APU POWER APU SHUTDOWN. FAULT LIGHT ILLUMINATED AFTER SEVERAL MINUTES THE FAULT LIGHT WENT OUT. THE APU SWITCH WAS IN THE OFF POSITION MOVED THERE AFTER THE APU SHUTDOWN. ACFT GROUNDED. R & R APU OIL COOLER, REF AMM 49-91-41-400--801 & 49-91-41-400-801. APU OPERATION AND LEAK CHECK OK.