TIMS showed Smoke External Alarm at car1603. Staff(AMK) checked and confirmed no signs of smoke / f ire / burning smell on exterior or interior of train. Rear T 420 line clear and confirmed no abnormalities. ~~~~~ TIMS showed Smoke External Alarm at car 1603(fault happrened twice). Staff(AMK) checked and confirmed no signs of smoke / fire / burning smell on exterior or interior of train. Rear T420 line clear and confirmed no abnormalities. CE: 1603 Smoke External Alarm able to reset No abnormality.  #1603 no.2 end external smoke detector replaced and function checked ok. Notification: 2580471 Done by: Saini/Din 15.3.24