TIMS showed Smoke External Alarm at car2687. Staff(AMK) checked and confirmed no signs of smoke or fire on exterior or interior of train. Rear T409 line clear and confirmed no abnormalities. ~~~~~ TIMS showed Smoke External Alarm at car FC-721 Smoke detector have sign of rusty on pcb,but no water imgress.C/O as preventive measure.Function test ok.Plaseal done. Not: 2482392 raise. Done by Koh/Sanip/Firdaus. 23/04/23