[b1mcp]

My advice would be to do some proper diagnostic work. Guessing at faults and replacing parts is an expensive process.

If you have access to VIDA then there are lots of other tests you can do apart from just reading codes.

You can look at live data for sensors and compare to expected values or other sensors.

You can activate components like relays, motors, pumps etc to see if things are working.

That's what I would be doing.