TC informed that TIMS showed 'obstacle detected' present on front DT car 'A4' door. TC updated that fault only occurs when train doors were open at platform andfault is extinguished when train doors were closed. Staff(K  ~~~~~ 3709 TC informed TIMS showed 'obstacle detected' @A4 door. TC updated that fault only occurs when train doors were open at platform and fault is extinguished when train doors were closed. Staff(KRJ) notified that when the aforementioned train doors were opened at platform, both train door leaves were about a quarter unopened, door was not fully opened. Pax flow was unaffected. TC at ADM SB, informed that fault had extinguished from TIMS. Staff(SBW) boarded the train and informed that no train door irregularities were found. CE: N , Depo to check (OE)  3709 found no door related FC. D/L ER & found no abnormalities with the DIR.    Checked door close s/w & door locking s/w - OK. Push/pull gauge check on door leaves - OK (7kg). Manually open/close doors & operation was smooth. Checked motor current, weather strip & door leading edge rubber gap (64mm) - OK. Cleaned J-rails. Found scratch marks on door bottom guide rails. Checked for FOD - Not found. Suspect FOD. Swapped #3709 A4 DCP to #3709 B3 as preventive measure.  Kwa ZY 44780