As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FIRE EXTINGUISHER SYSTEM INOP. INSPECTED APU COMPT FOR ANY SIGNS OF FIRE OR LEAKS, NONE FOUND LOOKS PRISTINE. REMOVED AND REPLACED THE APU FIRE BOTTLE AND OPS CHECKED NORMAL PER MM 26-22-02-4 AND GMM 9-4-403. AS A PRECAUTION ALSO REPLACED K602 APU AUTO FEXT RELAY REF WDM 26-22-21. ALL CHECKED NORMALLY.