1. Poor combustion condition
Poor engine combustion condition is the main reason why the engine trouble light comes on.
2. Engine knocking
There are generally three situations:
The first situation: the car is powerless;
The second situation: The car is weak and the noise of the engine is too loud;
The third situation: there is an obvious knocking noise in the cylinders.
In the first case, some engine malfunction lights will come on and others will not. In the second and third cases, the engine malfunction light will definitely turn on.
3. Internal reasons why the engine trouble light comes on
(1) Poor fuel quality
(2) The inside of the engine cylinder is not clean and there are carbon deposits.