TC reported Front M1 car smoke external.Rear T423 line clear no abnormalities. Staff(AMK) checked n o sign of smoke at external T256 Front M1 car. TC reported F ront M1 car smoke external. Rear T423 line clear no abnormal ~~~~~ TC reported Front M1 car smoke external.     Check and found smoke sensor dirty and sign of rusty.Change out as preventive measure.Function tested ok. Done by Sanip/Koh/Rizman.  08/01/24