TC reported BCU fault at RM1 car 1670. Train stopped while proceeding back to UPD TB1. Fault self cl eared. ~~~~~ 1670 TC reported BCU fault. Train stopped while proceeding back to UPD TB1. Fault self cleared.  1670 ACU replaced. Function test - OK. Brake pressure check & pneumatic system check - OK (refer to attached checklist). 1670 ACU S/N : OLD : 1442/057 NEW : 1549/214  Alcus/Alan 43859