As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN POSITION TO TAKEOFF, APU FIRE WARNING CAME ON. PULLED APU FIRE WARNING SWITCH. EMERGENCY FIRE TRUCK ESCORTED TO GATE. NO FIRE EVIDENT. APU SWITCH OFF. INSPECTED AND FOUND NO EVIDENCE OF FIRE. REMOVED AND REPLACED FIRE WARNING CONTROL PANEL AND APU BOTTLE AS PER BOEING MM.