What was found
DURING CLIMBOUT RECEIVED SMOKE TOILET CAUTION MESSAGE. COMPLETED NON-NORMAL CHECKLIST. FA REPORTED LAV SMOKE DETECTOR WENT OFF FOR COUPLE MINUTES AND THERE WAS A MUSTY BURNING ODOR IN CABIN. NO SMOKE/FIRE IN LAV. RETURNED TO DTW AFTER CONFERRING WITH DISPATCH. SMOKE TOILET CAUTION WAS ONLY ON FOR 3-4 MINUTES THEN EXTINGUISHED (BLEEDS OFF ENG IN TO). REMOVED AND REPLACED LAV SMOKE DETECTOR IAW AMM 26-16. PN ON/OFF PU90-421R3. RAN BOTH PACKS SUPPLIED APU AND BOTH ENGINES FOR 30 MINUTES ON GROUND AND COULD NOT DUPLICATE MUSTY SCENT. OPS TEST OF SMOKE DETECTOR IAW AMM 26-61. ALL CHECKS GOOD.