What Causes the Engine Malfunction Light to Flash Yellow?

[McKinsley]

When the engine malfunction light flashes, it indicates a fault in the engine, and the issue is relatively severe, requiring immediate inspection. The specific reasons may include the following seven: Sensor malfunction: The sensors referred to here include those for 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, which will trigger the engine malfunction light. Fuel quality issues: If fuel and engine oil are not added according to the manufacturer's requirements, it may cause engine wear and trigger the malfunction light. Poor combustion of the air-fuel mixture: Poor combustion can lead to engine carbon deposits or knocking. When detected by the oxygen sensor and reported to the ECU, the malfunction light will illuminate as a warning. Issues such as spark plug failure, ignition coil failure, fuel pump failure, or fuel line blockage can all cause poor combustion of the air-fuel mixture. Turbocharging issues: The intake turbocharging pipeline and turbocharger can also trigger the engine malfunction light. The most common issue is turbocharger damage, accompanied by symptoms such as oil leakage, high oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust. Intake issues: If there is a problem with the vehicle's intake, it may lead to engine pipeline blockage, and in severe cases, trigger the engine malfunction light. A dirty or uncleaned air filter can cause intake problems. Exhaust issues: Exhaust faults can also trigger the engine malfunction light. Common causes include rear oxygen sensor failure, catalytic converter issues, exhaust camshaft and bearing faults, with the catalytic converter being the most frequent. Using leaded gasoline, lead or silicon-containing lubricant additives, physical damage to the catalytic converter, or fuel system faults can easily cause catalytic converter failure. Anti-theft system malfunction: If the vehicle's electronic anti-theft system fails or the anti-theft controller does not match the engine electronic controller, the anti-theft system can prevent the engine from operating normally, and the malfunction light will illuminate. Generally, the engine malfunction light can display four states: steady yellow, flashing yellow, steady red, and flashing red. The severity of the fault increases from steady to flashing and from yellow to red. In order of severity: flashing red > flashing yellow > steady red > steady yellow. If the engine malfunction light illuminates, follow these steps: First, check whether the engine is running normally and if there are issues such as shaking or black smoke. If so, avoid restarting the engine. Particularly, do not restart the engine if the red light is on. If the engine can be started, turn it off for 5-10 minutes, then press the start button without pressing the brake, or turn the key halfway to the 'on' position without pressing the clutch. The vehicle will perform a self-check after powering on. Observe whether the malfunction light turns off after 5-10 seconds. If the light remains on, visit a service center as soon as possible. The service center can use a portable diagnostic tool to read the fault code, identify the issue, and perform targeted repairs.