TIMS showed Smoke External Alarm at car1509. Staff(AMK) checked and confirmed no signs of smoke / f ire / burning smell on exterior or interior of train. Rear T 216 line clear and confirmed no abnormalities. ~~~~~ 1509 To c/o No 1 internal smoke detector. #1509 checked and found internal smoke detector dusty. Serviced FSD and replaced new sensor (mushroom). Function check tested satis. Notification to CSC: 2517330 Done by Haslan, Asruddin. 22/8/2023. 1509 TIMS showed Smoke External Alarm. Staff(AMK) confirmed no signs of smoke/fire/burning smell on exterior or interior of train. Rear T216 line clear and confirmed no abnormalities. CE : Smoke Internal reset ok.  1509 FC smoke internal. Mainline TIMS show smoke internal no.1 end detected. FCP previously swapped on 14/7/23 to 3509 for same fault on 1509. Scope checked 1509 no.1 end internal smoke detector duct no dust clogged or water ingress. Ops 20 to check & replace 1509 no.1 end internal smoke detector.  Lee JC 45145