What was found
ON SHORT FINAL LOWER CARGO FIRE LIGHT CAME ON. DECLARE EMERGENCY AND CALLED FOR FIRE TRUCKS. AIRCRAFT LANDED WITHOUT INCIDENT. Performed troubleshooting, found MTX display codes FB15785(a), AC15722, AD11039, and AD12614 ratio too low. Removed and Replaced CCU IAW MM 26-15-01-2. Reprogrammed configuration module, ops ckd cargo compartment smoke detection system IAW MM 26-15-00-7 and STC ST00746LA-D found normal.