As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CARGO BTL LOW CAUTION MESSAGE ILLUMINATED IN FLIGHT. THE CREW RETURNED TO CLT WHERE MAINTENANCE DEFERRED THE CARGO FIRE EXTINGUISHING SYSTEM IAW MEL 26-25-01C AND RELEASED THE AIRCRAFT FOR SERVICE. MAINTENANCE IN TYS REMOVED & REPLACED THE LT CARGO COMPARTMENT FIRE BOTTLE IAW CRJ200 AMM 26-25-01-400(000)-801. THE OPERATIONAL CHECK WAS GOOD. THE MEL WAS CLEARED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.