Diagram looks good. The ECM also communicates with the MCM with IMA (MIMA) signals but not using any serial data ASFAIK.
Can't remember if you have the inverted/non inverted the right way round. But if it doesnt work one way just swap them round
I have the BCM Interceptor board which can sit on the BATTSCI or METSCII bus and be programmed to interact to fake BCM data or gauge data as we wish. My long term aim is to get rid of the stock BCM but that's not so easy as it gathers a lot of info which any replacement would also have to do.
You have a nice website with interesting projects. Just a word of advice on the BMS. The Insight IPU compartment is one of the noisiest pleces I have ever seen from an EMIRFI point of view. It took me 6 months to get my BMS to work in it!
Please keep us updated with your progress.
