ECU location on 2007 Lexus RX350 RHD Australian model

Question

After replacing the B2S1 O2 sensor the code remains and Ive now ruled out Sensor and looking towards wiring or ECU ECM PCM issues. Wondering where I can find the ECM & info on what pins I can test on ecu if I can locate the correct PCM,ECM,ECU as it seems every component is an ECU and pinpointing the correct module is tricky.

BTW Thanks for all your help so far its very much appreciated and I will certainly be donating when I get this thing up and running.