TC reported there is a brake BCU fault at car 1684 every time the train dwell at stations. Fault wil l clear when train depart stations. ~~~~~ 1684 TC reported there is a brake BCU fault at every time the train dwell at stations. Fault will clear when train depart stations. CE checked & found 1684 Intermittent BCU Fault.  1684 found FC 308 (BCU Fault), 330 (BCU BCP Fault Bogie 1), 331 (BCU BCP Fault Bogie 2). Found abnormal BCP reading on #1684 on ER, BCP braking was lower than other M cars by average of about of 0.5 bar. Checked/found #1684 ACU having air leakage. Swapped #1684 ACU (S/N:0539/170) swapped with #2684 (S/N:1538/158). Replaced new ACU on #2684 (S/N:1516/106). Brake cyclic test & brake application/release checked - OK. Brake pressure check on #1684 & #2684 - OK. #1684 AS pressure = 2.92 bar.  Ridzuan/Abdillah/Faizal 44986