Part of the problem is how insanely complex modern cars are. Modern cars can have 30+ different ECUs, and knowing which ECU does what can be difficult to figure out. Programming ECUs is also a bit of a dark art, and a model line of cars can go through a number of ECU versions over time.

I used to own a car that the battery regularly died on. Eventually, after multiple dealer visits, a couple replaced batteries, and hours of internet research, I found two service recalls that described my cars symptoms perfectly. The problem for me was my cars VIN fell outside both recall notices. But I took printouts of both recall notices to a dealer and they agreed to look into it. They confirmed my car had buggy firmware, annd ended up installing updated firmware on two different ECUs. I never had a battery problem again after that. I’ve worked in tech for 30+ years and I wouldn’t have wanted to tackle that on my own…