TC reported obstacle detected alarm at front M1 car A3 door. Staff(RFP) checked and confirmed front M1 car 'A3' door did not opened. Staff(RFP) later isolated t he defective train door in closed position. ~~~~~ 1646 TC reported obstacle detected alarm @A3 door. Staff(RFP) confirmed 1646 'A3' door did not opened. Staff(RFP) isolated the defective train door in closed position. CE: 1645 A3 door isolated. 1646 A3 door ok.  1645 A3 door performed the following checks : FOD found: N Weather strip condition ok: Y Roller condition ok: N, 1645 A3 LHS outer roller delam Clean J-rail & guide rail: Y Door cyclic test 20x, DIR extinguish ok: Y, after rectification TIMS door static timing test pass: Y, after rectification Door lock switch red line flush: Y Door close switch actuating plate distance ok: Y Replaced #1645 door outer rollers to iron rollers.  Aliff/Daniel/Redzwan/Chan SW 45399