Modern vehicles are essentially rolling computers. When a check engine light...

https://mike-wiki.win/index.php/Why_Modern_Cars_Need_Software_for_Fuel_Injection_Issues

Modern vehicles are essentially rolling computers. When a check engine light pops on, basic OBD readers only give you a surface-level code. To actually fix the car, you need to talk to every ECU and view live data streams while the engine runs