TIMS showed Smoke External Alarm at car1518. Staff(YCK) checked and confirmed no signs of smoke / f ire / burning smell on exterior or interior of train. Rear T 262 line clear and confirmed no abnormalities. TIMS showed S ~~~~~ TIMS showed Smoke External Alarm at car 1518. Staff(YCK) checked and confirmed no signs of smoke / fire / burning smell on exterior or interior of train. Rear T262 line clear and confirmed no abnormalities. CE: 1518 smoke external reset ok no abnormality found  Check and found smoke external very dirty and PCB side having rusty. Change out smoke external unit and function test ok. Done by Faiz/koh 21.03.2024