What does it mean when the engine light turns yellow?

[DiHazel]

When the engine light turns yellow, it indicates a fault in the engine. The reasons may include: 1. The gasoline used is of poor quality or there is excessive carbon buildup in the engine, leading to poor combustion conditions, which may trigger the fault light. In such cases, it is important to promptly inspect the engine. 2. A malfunction in the engine's oxygen sensor usually causes the engine fault light to turn yellow. While it may not affect normal driving, it should still be checked promptly. 3. Issues such as clogged fuel injectors or carbon buildup in the intake valves can also trigger the fault light. These problems are often related to the quality of the fuel used or dust entering during car maintenance. Fuel quality is a primary factor causing the engine fault light to illuminate. For example, 97-octane gasoline should have an octane rating of no less than 97. Leaded gasoline can cause lead poisoning in the oxygen sensor, making fuel quality a major reason for insufficient engine combustion, which in turn triggers the engine fault light.