What Causes the Engine Fault Yellow Light to Stay On?
3 Answers
When the engine yellow fault light is on, it means a warning, indicating that some system parameters of the car may exceed the set range. At this time, the car can continue to drive, but some functions may be limited. The engine fault light can also be red. When the red fault light is on, it means prohibition. At this time, the car must stop immediately, turn off the engine, and prohibit continued driving, and check where the fault occurred. There are mainly the following 7 reasons for the engine fault light to stay on: Sensor failure: The sensors mentioned here include water temperature, crankshaft position, air flow, intake temperature, oxygen sensor, etc. When these sensors are damaged, have poor contact, or signal interruption, the car's ECU cannot accurately obtain engine data, which will cause the engine fault light to come on. Oil quality issues: If fuel and engine oil are not added according to the manufacturer's requirements, it may cause engine wear and trigger the fault light. Poor combustion of the air-fuel mixture: Poor combustion of the air-fuel mixture can lead to engine carbon deposits or knocking. After being detected by the oxygen sensor and reported to the ECU, the fault light will come on as a warning. Spark plug failure, ignition coil failure, fuel pump failure, and fuel line blockage can all cause poor combustion of the engine air-fuel mixture. Turbocharging issues: The intake boost pipeline and turbocharger can also cause the engine fault light to come on. The most common is turbocharger damage, accompanied by symptoms such as oil leakage, high oil consumption, reduced power, metal noise, and blue or black smoke from the exhaust pipe. Intake issues: If there is a problem with the car's intake, it may cause engine pipeline blockage, and in severe cases, trigger the engine fault light. A dirty air filter that is not cleaned regularly can lead to intake problems. Exhaust issues: Exhaust faults can also cause the engine fault light to come on. The rear oxygen sensor, three-way catalytic converter, exhaust camshaft, and bearing failure are all causes of exhaust problems, with the three-way catalytic converter being the most common. Using leaded gasoline, lead or silicon-based lubricant additives, physical damage to the three-way catalytic converter, and engine fuel supply system faults can easily cause three-way catalytic converter failure. Anti-theft system failure: If the car's electronic anti-theft system fails, or the anti-theft controller does not match the engine electronic controller, the anti-theft system can also cause the engine to malfunction and trigger the fault light. If the engine fault light is on, you can follow these steps: First, check if the engine is running normally and if there are any issues like shaking or smoke. If so, try not to restart the engine. Especially note that if the red light is on, do not restart the engine. If the engine can be started, turn it off for 5-10 minutes, then 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 perform a self-check after powering on. Wait for 5-10 seconds and observe if the fault light on the dashboard turns off. If the fault light does not turn off, please visit a service station as soon as possible to identify the cause. The service station can use a portable diagnostic tool to read the fault code, obtain fault information, and perform targeted repairs.
Last time I was driving, I was startled to find the yellow engine malfunction indicator light (MIL) staying on constantly. After inspection, I learned there could be multiple causes. Common issues include faulty engine sensors, such as a malfunctioning oxygen sensor which monitors exhaust emissions - its failure triggers the light. Ignition system problems like misfiring spark plugs or fuel system issues such as clogged injectors causing insufficient fuel supply may also be culprits. Additionally, if the emission control system malfunctions, like reduced efficiency of the catalytic converter, the light remains illuminated. Neglecting repairs may lead to severe engine shaking, significantly increased fuel consumption, and even greater environmental pollution. I recommend immediately visiting a repair shop to scan for trouble codes using an OBD scanner to pinpoint the exact cause. Regular maintenance with attention to sensor cleanliness can prevent many issues. An illuminated engine light is no trivial matter - never delay addressing it, as safety comes first.
As someone who frequently works on cars, I must say that the engine malfunction indicator light (MIL) staying illuminated in yellow is quite common. The most frequent cause is a faulty oxygen sensor, as it monitors the oxygen content in the exhaust; when it fails, the light comes on to indicate an issue. Next are ignition system problems, such as failing spark plugs or ignition coils, or issues with the emission control system, like a stuck EGR valve causing poor exhaust gas recirculation. On the fuel side, carbon buildup clogging the fuel injectors can also trigger the warning light. While driving, you might notice reduced power and unstable acceleration. Don't underestimate this issue—ignoring it can lead to skyrocketing fuel consumption, engine damage, and increased emissions. A simple solution is to visit a professional shop where they can use a diagnostic tool to scan for trouble codes, quickly identify the cause, and replace the faulty parts. For maintenance, regular sensor checks and fuel system cleaning are recommended to prolong component lifespan.
