What happened to the car trouble light?

The reasons why the vehicle fault light does not light up are: 1, too much carbon deposit in the throttle or engine; 2. The oxygen sensor fails, resulting in unbalanced mixing ratio. If you drive at a low speed in the downtown area for a long time, it is easy to appear this phenomenon; 3. The nozzle leaks oil, causing the nozzle to remain in the oil supply state after the throttle valve is closed, resulting in too much mixed gas when driving at low speed, which leads to unstable idle speed after the fuel is closed. If it is serious, turn it off directly; 4. The oxygen sensor was poisoned by adding inferior gasoline with excessive metal content. The solution is to change to a gas station.