TIMS showed fire external but did not show which saloon car. Rear train 218 line cleared and confirm ed no abnormality. SM(AMK) checked and confirmed no abnormal ity on train 217. TIMS showed fire external but did not show ~~~~~ TIMS showed fire external but did not sh   #3566 checked and found external smoke detector unit dusty, replaced smoke detector and function test ok. Notification to CSC: 2576289 Done by: Ngieng, Fazil, Kumar (2/3/24)