What is the reason why the fault light of Audi Q7 engine is on?

Generally, the engine fault light is on, and it may be that the combustion state is not particularly good. General engine condition is not good, which is the main reason for the engine fault light. There is also an engine warranty, which will also cause the fault light to light up, such as the car is weak, the engine noise is too loud, or there is obvious knocking sound. So we still need to do some regular maintenance and repair.