What Causes the Engine Malfunction Light to Stay On?
3 Answers
The engine malfunction light may stay on due to the following 7 main reasons: 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 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 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. Spark plug failure, ignition coil failure, fuel pump failure, and fuel line blockage can all cause poor combustion of the air-fuel mixture. Turbocharging issues: The intake turbocharging pipeline and turbocharger can also cause the engine malfunction light to illuminate. The most common issue is turbocharger damage, accompanied by symptoms such as oil leakage, high oil consumption, reduced power, metallic noises, 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 malfunction light. A dirty air filter that is not cleaned regularly can lead to intake problems. Exhaust issues: Exhaust faults can also cause the engine malfunction light to illuminate. 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-containing lubricant additives, physical damage to the catalytic converter, or faults in the engine fuel supply system can easily cause catalytic converter failure. Anti-theft system malfunction: If the car's electronic anti-theft system malfunctions or the anti-theft controller does not match the engine electronic controller, the anti-theft system can also prevent the engine from operating normally, while illuminating the engine malfunction light. If the engine malfunction light is on, follow these steps: First, check if the engine is running normally and if there are any issues such as shaking or smoke. If so, avoid restarting the engine. Especially note that you must not restart the engine if the red light is on. 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 depressing the clutch. The car will perform a self-check after powering on. Wait for 5-10 seconds and observe if the malfunction light on the dashboard turns off. If the malfunction light remains on, visit a service center as soon as possible to identify the cause. The service center can use a portable diagnostic tool to read the fault codes, obtain fault information, and perform targeted repairs.
I've encountered this issue too. A constantly illuminated engine warning light is indeed a headache. Common causes include sensor problems, such as a faulty oxygen sensor that can make the computer misjudge excessive emissions. There are also minor issues like a dirty throttle body or aging spark plugs - excessive carbon buildup can affect combustion efficiency. Poor fuel quality is another hidden culprit; long-term use of substandard fuel can clog fuel injectors. When repairing cars myself, I've found the most easily overlooked issue is an improperly tightened fuel cap - gasoline vapor leakage can also trigger the warning light. Physical faults like aged or damaged wiring also need checking, especially in older vehicles. Finally, there could be emission system failures, like a clogged catalytic converter or stuck EGR valve. My advice: don't delay. The most straightforward solution is to visit a dealership and connect a diagnostic scanner to read the trouble codes, preventing minor issues from turning into major repairs.
The engine malfunction indicator light turning on is like the car running a fever, requiring careful diagnosis of the root cause. From my research, 80% of cases are caused by sensor failures, particularly the intake manifold pressure sensor and crankshaft position sensor being the most prone to issues. Another common cause is incorrect air-fuel mixture ratio leading to incomplete combustion. For turbocharged models, special attention should be paid to unique failures like stuck turbo wastegates. A car owner friend experienced light activation after using ethanol-blended gasoline - fuel incompatibility can also trigger this. Electrical issues such as unstable battery voltage or insufficient alternator output may also cause it. Cooling system problems can indirectly lead to this too, like water pump leaks causing engine overheating. Many owners overlook the possibility of needing ECU software updates. Regular intake tract carbon cleaning effectively prevents this issue, since heavy carbon buildup can lead to various problems.
