What Causes the Engine Malfunction Light to Turn Yellow?

[VanRachel]

The engine yellow warning light indicates a warning, meaning that certain system parameters of the vehicle may have exceeded the set range. At this time, the vehicle can continue to drive, but some functions may be restricted. The engine malfunction light can also be red. A red malfunction light indicates a prohibition, meaning the vehicle must stop immediately, turn off the engine, and refrain from further driving while checking for the source of the malfunction. There are seven main reasons why the engine malfunction light may illuminate: Sensor malfunction: This includes sensors such as the coolant temperature sensor, crankshaft position sensor, air flow sensor, intake air temperature sensor, and oxygen sensor. When these sensors are damaged, have poor contact, or their signals are interrupted, the vehicle's ECU cannot accurately obtain engine data, which can trigger the engine malfunction light. Fuel or oil quality issues: If the fuel or engine oil is not added as required by the manufacturer, it may cause engine wear and trigger the malfunction light. Poor combustion of the air-fuel mixture: Poor combustion can lead to 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 pump failures, or clogged fuel lines can all cause poor combustion of the air-fuel mixture. Turbocharger issues: Problems with the intake boost pipes or turbocharger can also trigger the engine malfunction light. 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 problems: If there is an issue with the vehicle's intake system, it may lead to clogged engine pipes, and in severe cases, trigger the malfunction light. A dirty or uncleaned air filter can cause intake problems. Exhaust problems: Exhaust system failures can also trigger the engine malfunction light. Common causes include faulty rear oxygen sensors, catalytic converters, exhaust camshafts, or bearing failures. The catalytic converter is the most frequent culprit. Using leaded gasoline, lead- or silicon-containing lubricant additives, physical damage to the catalytic converter, or fuel system malfunctions can all lead to catalytic converter issues. Anti-theft system malfunction: If the vehicle's electronic anti-theft system malfunctions or if the anti-theft controller does not match the engine's electronic controller, the anti-theft system can prevent the engine from operating normally and trigger the malfunction light. If the engine malfunction light illuminates, follow these steps: First, check whether the engine is running normally and if there are any issues such as shaking or smoke. If so, avoid restarting the engine. Note: If the red light is on, do not restart the engine under any circumstances. If the engine can be started, turn it off and wait 5-10 minutes. Without pressing the brake, press the start button once or turn the key halfway to the "ON" position without depressing the clutch. The vehicle will perform a self-check after powering on. Wait 5-10 seconds and observe whether the malfunction light on the dashboard turns off. 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.