TIMS showed Smoke External Alarm at car 2508. Train end service at AMK. TC when changing end feedbac ked no signs of smoke on exterior or interior of train. RearT416 line clear and confirmed no abnormalities. TIMS showed  ~~~~~ TIMS showed Smoke External Alarm at car 2508. Train end service at AMK. TC when changing end feedbacked no signs of smoke on exterior or interior of train. Rear T416 line clear and confirmed no abnormalities.  Check the above mention reported FC 721. Replace smoke detector due to smoke detector dirty. Conduct functional check and security check ok Notif:2609706 Done by Saini/Morgan 45463