3531 BCU fault. To check * rectify. ~~~~~ 3531 BCU fault.  3531 ACU replaced - Done. Function test - OK. Brake pressure test - oK. Air leak test 0.4 bar/5 min - OK.    3531 ACU S/N : OLD : 12/119/045 NEW : 1311/058  Selvan/Lee PT 43972