What Causes the Engine Light to Turn Yellow?
2 Answers
The engine light turning yellow can be caused by various reasons, including poor fuel quality, engine knocking or detonation, or a damaged water temperature sensor. Poor fuel quality: If the olefin content is too high, it can produce gummy substances during use, which accumulate in the intake manifold and valve guide areas. When the engine is shut off and cools down for a period, these deposits can stick the valves to the valve guides. Upon restarting the engine, this can lead to valve sticking. Engine knocking or detonation: When the level of imperceptible knocking exceeds the range that the engine control unit (ECU) can adjust, the engine fault light will illuminate as a warning. Damaged water temperature sensor: The water temperature sensor contains a thermistor, which has higher resistance at lower temperatures and lower resistance at higher temperatures. When the engine coolant is cold, the sensor sends a signal to the ECU to enrich the air-fuel mixture, ensuring stable engine operation. If the sensor fails to provide this cold-engine state information, the air-fuel mixture may become too lean, causing unstable engine performance.
The other day while driving, I noticed the engine yellow light came on, which is actually quite common and mainly triggered by issues with the emission system. The most frequent culprit is a faulty oxygen sensor, which monitors the oxygen levels in the exhaust. If it malfunctions, it triggers an error and may result in increased fuel consumption. Alternatively, there might be minor issues with the fuel system, such as a loose fuel cap, causing an imbalance in the system pressure. Worse yet, it could be worn spark plugs or faulty coils in the ignition system. I recommend first checking if the fuel cap is tightened properly. If the light persists, it's best to visit a repair shop to diagnose the issue using a code reader. Ignoring it could lead to problems spreading to more expensive components, like the catalytic converter, making repairs much more complicated. Regular vehicle maintenance can help prevent these issues from occurring.
