721/722 both cab self test fail(Train pr ~~~~~ 721/722 both cab self test fail     From #721 side,brake self test fail.Conduct parking brake test ,application ok,when release parking brake #3721 BCU unit ok and 2 fault appear.Event log show internal Aux 1 pressure sensor is open circuit.Replace RIO v/v bogie 2 function test parking brake,BCU unit ok.One fault at #3721 and #2721 BCU unit healthy 2 fault.Conduct self test still show fault. Compare RIO v/v having different version.To further check. RIO v/v-New s/n: 1948116  Old s/n: 1802094 0020 raise to replace RIO v/v. Done by Koh/Saini/Asruddin. 06/04/21,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, To further investigate #3721-Bogie 2 replace RIO v/v.Parking brake test ok.Service brake test ok.Self test-pass. Car #3721-RIO v/v.    New s/n: 1806107 Old s/n: 1948116 Done by Koh/Haslan/Asruddin. 7/04/21