What Causes the Engine Malfunction Light to Turn Yellow After Refueling?
2 Answers
The reason the engine malfunction light turns yellow after refueling is: the gasoline quality does not meet the standard. After adding high-quality fuel, the engine malfunction light will turn off by itself after about 30 seconds of running the engine. The causes of engine malfunction are: 1. Oxygen sensor failure; 2. Intake pipe leakage leading to overly lean air-fuel mixture; 3. Turbocharger system failure; 4. Low fuel pressure, clogged fuel injectors or fuel filter; 5. Abnormal signals from pressure sensor or throttle position sensor; 6. Sensor signal abnormalities causing incorrect ignition timing or delayed ignition; 7. Weak high-voltage spark due to faulty spark plugs, ignition coils, or high-voltage wires; 8. Dirty throttle body; 9. Poor operation of the exhaust gas recirculation system; 10. Clogged exhaust pipe; 11. Low cylinder pressure.
I've encountered the situation several times where the engine malfunction indicator light (yellow) came on after refueling, which is quite common. Usually, it's because the fuel tank cap wasn't tightened properly, and it got loose during refueling without noticing, causing the system to think there's a fuel vapor leak and trigger an alarm. It could also be due to filling up with contaminated fuel, such as poor-quality gasoline from small gas stations, leading to sensor false alarms or clogged fuel injectors. I've experienced it myself—re-tightening the cap and driving for a few minutes made the light go off. But it's best to develop a habit of checking the cap after refueling. If the light doesn't go off or keeps coming back on, deeper issues need to be considered, such as a faulty oxygen sensor or fuel pump problem. These require diagnosis with a professional scan tool at a repair shop. Remember not to keep driving with the light on—while a yellow light isn't as urgent as a red one, it still indicates a potential issue that needs attention. Safety first.
