TIMS showed Smoke External Alarm at car2525. Staff(YCK) checked and confirmed no signs of smoke / f ire / burning smell on exterior or interior of train. Rear T 409 line clear and confirmed no abnormalities. ~~~~~ TIMS showed Smoke External Alarm at car 2525. Staff(YCK) checked and confirmed no signs of smoke / fire / burning smell on exterior or interior of train. Rear T409 line clear and confirmed no abnormalities. CE: 2525 smoke external alarm able to reset No abnormality  Check and found smoke external sensor very dirty, clean up and check PCB no sign of rusty/water ingress. Function test ok Done by Snip/Rizman/Koh 29.03.2024