What to Do When the Engine Malfunction Light Comes On After Refueling?
2 Answers
If the engine malfunction light comes on after refueling, it indicates that low-quality fuel has been added. During the combustion process in the engine, due to the high impurity content and low combustion efficiency of low-quality fuel, some impurities and unburned fuel accumulate in the combustion chamber, occupying space and causing the engine malfunction light to illuminate. Solution: Promptly drain the low-quality fuel and clean the fuel tank and fuel lines. After cleaning, replace it with high-quality fuel. Apart from fuel quality issues, other reasons that may cause the engine malfunction light to come on include: Sensor Malfunction: The sensors mentioned here include coolant temperature, crankshaft position, air flow, intake temperature, oxygen sensors, etc. When these sensors are damaged, have poor contact, or experience signal interruption, the vehicle's ECU cannot accurately obtain engine data, leading to the illumination of the engine malfunction light. Poor Combustion of Air-Fuel Mixture: Poor combustion of the air-fuel mixture can cause engine carbon buildup or knocking. When detected by the oxygen sensor and reported to the ECU, the malfunction light will illuminate as a warning. Issues such as faulty spark plugs, ignition coils, fuel pumps, or clogged fuel lines can lead to poor combustion of the air-fuel mixture. Turbocharger Issues: Problems with the intake boost pipes or turbocharger can also cause the engine malfunction light to come on. The most common issue is a damaged turbocharger, accompanied by symptoms such as oil leaks, excessive oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust. Intake Issues: If the vehicle's intake system has problems, it may lead to clogged engine pipes, and in severe cases, trigger the engine malfunction light. A dirty air filter that is not cleaned regularly can cause intake issues. Exhaust Issues: Exhaust system faults can also cause the engine malfunction light to illuminate. Common causes include faulty rear oxygen sensors, catalytic converters, exhaust camshafts, or bearings. The catalytic converter is the most frequently affected component. Using leaded gasoline, lead- or silicon-based lubricant additives, physical damage to the catalytic converter, or fuel system malfunctions can easily lead to catalytic converter failure. Anti-Theft System Malfunction: If the vehicle's electronic anti-theft system malfunctions or if the anti-theft controller does not match the engine electronic controller, the anti-theft system can prevent the engine from operating normally and trigger the engine malfunction light.
I had the exact same issue two years ago! The light came on right after refueling with 95-octane gas. Don't panic yet—first check if the fuel cap is tightened properly. A deformed rubber seal or improperly tightened cap can trigger the fault code. In my case, the light went off only after I re-tightened it until I heard three 'clicks'. Also, check the fuel quality—stratified fuel from small gas stations may cause false readings from the rear oxygen sensor. If the light stays on after two days, it's likely the fuel injectors are clogged with debris. Remember not to wait until the fuel gauge hits empty before refueling, as sediment at the bottom of the tank can get sucked up. I finally cleared the light by driving at high speed for half an hour, but if it stays on persistently, you must visit the 4S shop to read the fault codes.
