TC feedback rear M2 car smoke external pre alarm. Staff(CNG) check and confirm no smoke ,no heat, noabnormalities. ~~~~~ CHECKED AND FOUND #3507 AND #2507 SMOKE EXTER L FAULT IN TIMS. RESET BOTH EXTER L SMOKE AND MONITOR FOR 1 HR. CHECKED AND FOUND #3507 SMOKE EXTER L TRIGGERED. REPLACED #3507 EXTER L SMOKE DETECTOR UNIT. CONDUCTED FUNCTION TESTED OK. CHECKED HATCH COVER #3507 OK. MURALI/HAIRUL/SOLLEHIN/ZAHIR 03/01/21.