1503 During DT found BCU fault. ~~~~~ 1503 During DT found BCU fault.  1503 ER D/L - Done. Replaced 1503 ACU - Done. Brake pressure test & air leak test (0.5 bar/5 min) - OK (refer to attached record sheet). 1503 ACU S/N : OLD : 1037-056 NEW : 1264-108  Selvan 44041