Is there such a thing as as fault free engine answer no!
All manufacturers have their quirks some more than others
A modern car simply cannot be diagnosed without ann oscilloscope.Todays cars have a lot of very complex and fast signals
Oxygen sensors can only really be tested using an oscilloscope their reaction is vital to suit individual ecu needs.Scan tool data goes so far but doesn't give the whole picture
It as become a real myth that plugging in a code reader and hey presto out pops the answer is the way to go diagnosing your cars issues.
Steer away from any garage offering code reading you will find yourself playing the throw parts at the issue getting you no where
Lunar auto diagnostics