TC reported rear DT car B3 door not proven closed. TC open and close train doors - ok ~~~~~ Downloaded ER and fault trace data on PTU006. Checked #3682-B3 door guide rail and J-rail for F.O.D. Found lumps of dirt on J-rail, removed and cleaned. Service door rollers. Mesured door sensing s/w-ok. Push/pull gauge and door cyclic tested ok. Done by Kumar/Jack/Sateesh/Koh. 10/03/20.