TC reported External Smoke Pre-Alarm 2 in Rear M2 car. Staff (JKN) checked and confirmedno heat nosmoke found. ~~~~~ REFER OPS 20.   CHECK AND CONFIRM 2610 SMOKE EXTER L TRIGGER U BLE TO RESET. FURTHER CHECK FOUND 2610 NO.2 END SMOKE SENSOR UNIT FAULTY. WATER INGRESS. SWAP SMOKE SENSOR AND CONTROL UNIT AND FAULT STILL EXISTS. N.ALAI.M.K/03.01.21. ---------------------   REPLACED #2610 NO-2 END EXTER L SMOKE SENSOR UNIT. SECURITY    CHECK OK. CONDUCT FUNCTION TEST AND ABLE TO DETECT THE SMOKE ALARM IN TIMS & CONTROL PANEL. MONITOR AN HOUR NO ABNORMAL FOUND. NOTIFICATION NO: 2235656. OLD: NIL. NEW: SD-008.  SHAHRIE / BUDIMAN / ALBERADO, 04/01/2021.