Why Does the Engine Malfunction Light Keep Coming On?

[VonJuniper]

There are mainly 7 reasons why the engine malfunction light comes on: Sensor malfunction: The sensors mentioned here include coolant temperature, crankshaft position, air flow, intake air temperature, oxygen sensors, etc. When these sensors are damaged, have poor contact, or experience signal interruption, the car'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 as required by the manufacturer, it may cause engine wear, leading to the malfunction light coming on. Poor combustion of the 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. Spark plug failure, ignition coil failure, fuel pump failure, and fuel line blockages can all cause poor combustion of the engine's air-fuel mixture. Turbocharging issues: The intake boost pipeline and turbocharger can also cause the engine malfunction light to come on. The most common issue is turbocharger damage, accompanied by symptoms such as oil leaks, high oil consumption, reduced power, metallic noises, and blue or black smoke from the exhaust pipe. Intake issues: If the car's intake system has problems, it may lead to engine pipeline blockages, and in severe cases, the engine malfunction light will come on. A dirty air filter that is not cleaned regularly can cause intake problems. Exhaust issues: Exhaust system failures can also trigger the engine malfunction light. The rear oxygen sensor, catalytic converter, exhaust camshaft, and bearing failures are all causes of exhaust problems, with the catalytic converter being the most common. Using leaded gasoline, lead or silicon-based lubricant additives, physical damage to the catalytic converter, or engine fuel system failures can easily cause catalytic converter issues. Anti-theft system malfunction: If the car'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 the engine malfunction light will come on. If the engine malfunction light comes on, follow these steps: First, check if the engine is running normally and if there are any issues like shaking or smoke. If so, avoid restarting the engine. Note: Do not restart the engine if the red warning light is on. 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 pressing the clutch. The car will enter self-check mode after powering on. Wait 5-10 seconds to see if the malfunction light turns off on the dashboard. If the malfunction light remains on, visit a service station as soon as possible to diagnose the issue. The service station can use a portable diagnostic tool to read the fault code, obtain fault information, and perform targeted repairs.

[SanHaley]

I drive an older car, and the engine warning light keeps coming on, which is quite a headache. At first, I thought it was a faulty sensor in the exhaust system—the one that monitors emissions. If that fails, the light flashes. After replacing it, things improved a bit, but the light came back on within days. That’s when I realized it might be due to low fuel pump pressure or dirty fuel causing a rich air-fuel mixture. I tried using fuel additives to clean the fuel system, but the effect didn’t last. Later, I started doing regular maintenance, including oil changes and carbon deposit cleaning, and finally, the issue stabilized. If you ignore it, the car’s performance will weaken, and over time, it can damage the engine’s core components. My advice is to visit a professional shop to read the fault codes as soon as the light comes on. Don’t delay like I did—repair costs will end up being higher. Oh, and when air quality is poor, pay extra attention to the air intake system’s filtration, as dust can worsen the problem.