I work in the industry, but have no knowledge of those particular Bosch/VW projects. Yes the Tier-1 supplier is responsible for building the final software ima

I work in the industry, but have no knowledge of those particular Bosch/VW projects. Yes the Tier-1 supplier is responsible for building the final software image that runs on their ECU, and for some smaller OEMs the Tier-1 will write all the application software in addition to the basic platform software. However, it's not unusual for the bigger OEMs (such as VW) to develop parts of the application software themselves and provide it as object code for the Tier-1 supplier to link. This is effectively a black box as far as the Tier-1 is concerned.