As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER AIRCRAFT WAS PUSHED BACK FROM GATE AND APU SHUT DOWN, 'CHECK FIRE DETECT' WARNING LIGHT ILLUMINATED AND FAULT LIGHT ON APU FIRE DETECT PANEL ILLUMINATED. AIRCRAFT WAS RETURNED TO GATE WHERE MAINTENANCE INSPECTED SYSTEM. NO DEFECTS WERE NOTED AROUND THE FIRE DETECTION LINE OR FIRE BOTTLE. FIRE BOTTLE WAS NOTED AS BEING CHARGED. RELAY 2622-K3 WAS CHANGED ALONG WITH THE WARNING CONTROL BOX. OPS CHECKS WERE GOOD AND AIRCRAFT WAS RELEASED FOR SERVICE.