TIMS showed Smoke External Alarm at Front M1 car. Staff(AMK) checked and confirmed no signs of smokeexternal of train. Rear T226 line clear no abnormalities. ~~~~~ TIMS showed Smoke External Alarm at Fron Check and found external FSD PCB side rusty and smoke sensor very dusty to c/o and function test ok. #1550 external FSD:- Not: 2494554 raise. Done by Sanip/Koh. 04/06/23