Modern cars are rolling computers with dozens of interconnected ECUs that...

https://canvas.instructure.com/eportfolios/4205778/home/understanding-oem-protocols-why-your-shop-needs-more-than-a-generic-reader

Modern cars are rolling computers with dozens of interconnected ECUs that constantly talk to each other. A basic OBD reader only scratches the surface by pulling simple codes, but it won’t show you the live data streams needed to catch intermittent faults