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

https://www.cool-bookmarks.win/if-you-re-still-relying-on-a-basic-code-reader-you-re-only-seeing-half-the

Modern cars are rolling computers with dozens of interconnected ECUs that constantly talk to each other. When a dash light pops on, a basic OBD reader only gives you a vague fault code