I recall when I bought my first hybrid that the dealer said there were something like 15 different computers controlling things, from the ICE engine to the transmission to the charging of the battery, etc. They weren’t networked together.

I also once ran afoul of a software bug in the ECU of a Honda CR/V. That’s the embedded system that manages the whole operation of the engine - from fuel injection to timing to emissions etc. As they progress through model years they use different ECUs that require different software. Even though I work in IT, I wouldn’t feel comfortable trying to update it myself, given the different models, firmware revisions, etc. I was more than happy to take that car to a dealer to have them confirm my car had buggy software and to upgrade it to the right new version.