I specialised in new vehicles and then you have specialise in brand to actually know whats going on and how to fix said black boxes and systems.

My reason for training to become a software engineer was mainly because I felt like the knowledge and on-going training you need to retain/constantly learn was not worth the money earned.

Instead now I earn my bread from what was my hobby, essentially the same work ethic as far as knowledge is concerned just less back breaking to put into practice.