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

https://www.focus2move.com/why-diagnostic-software-has-become-essential-for-modern-vehicle-repairs/

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