Modern cars are basically rolling networks. Your basic OBD reader only gives...

https://wiki-triod.win/index.php/Why_Does_My_Check_Engine_Light_Keep_Coming_Back%3F_Stop_Clearing_Codes_and_Start_Fixing_Cars

Modern cars are basically rolling networks. Your basic OBD reader only gives you a surface-level trouble code, which is like guessing the sickness without looking at the symptoms