TC reported brake fault present in rearM2 car. TIMS showed 'BCU suspension fault', 'BCU command pre ssure', 'BCU fault' at bogie #1 and #2. Train performance - ok. TC reported at JUR EB, all cars have service brake excep ~~~~~ TO CONDUCT MAINLINE TEST.  677/678 M/L test conducted & passed. No sign of brake fault or stuck brake.  Lee JC 44715 2677 TC reported brake fault present. TIMS showed 'BCU suspension fault', 'BCU command pressure', 'BCU fault' at bogie #1 and #2. Train performance - ok. TC reported at JUR EB, when train stationary, all cars have service brake except for Rear M2 (2677)car. Thereafter, ECB activated when train was at CLE EB. Staff(CLE) feedback that there was smoke near rear M2 car. Pax disembarked to platform.    Train proceeded in ATPM to turnaround at QUE to return to UPD. Staff(CLE) on-board train isolated BIC in rear M2 car(2677).  2677 BCU swapped to #1677 & fault transferred. Replaced #1677 BCU & found ACU hunting sound. Replaced ACU & no leakage found. Function check brake status - OK. #1677 ACU S/N : OLD : 1516106 NEW : 1528125 (Faulty Spare) Replace again : 1439-027 (NEW) BCU S/N : OLD : 1541-283 NEW : 1521-194 Swapped #1677 BCU to #2677. Replaced #1677 ACU. Function check all brake status - OK. ACU S/N : OLD : 1439-027 NEW : 1442/034  Alan/Lee PT/Shafie/Kamarul 44713