The engine malfunction indicator light may illuminate due to the following 7 main reasons: Sensor failure: This includes sensors such as coolant temperature, crankshaft position, air flow, intake air temperature, and oxygen sensors. When these sensors are damaged, have poor contact, or experience signal interruption, the vehicle's ECU cannot accurately obtain engine data, triggering the malfunction indicator light. Fuel/oil quality issues: Failure to use the manufacturer-recommended fuel and engine oil may cause engine wear, leading to the illumination of the malfunction light. Poor fuel mixture combustion: This can cause engine carbon buildup or knocking. When detected by the oxygen sensor and reported to the ECU, the malfunction light will activate as a warning. Causes include spark plug failure, ignition coil malfunction, fuel pump issues, or fuel line blockage. Turbocharging problems: Issues with the intake boost system or turbocharger can trigger the light. The most common is turbocharger damage, often accompanied by oil leaks, excessive oil consumption, power loss, metallic noises, or blue/black exhaust smoke. Intake system problems: Air intake issues may lead to engine pipe blockages, potentially triggering the light. A dirty air filter that hasn't been regularly cleaned can cause intake problems. Exhaust system faults: These can also activate the light. Common causes include rear oxygen sensor failure, catalytic converter issues (most frequent), or exhaust camshaft/bearing problems. Leaded gasoline, improper lubricant additives, physical damage to the catalytic converter, or fuel system malfunctions often cause catalytic converter failure. Anti-theft system malfunction: If the electronic anti-theft system fails or the anti-theft controller doesn't match the engine ECU, the system may prevent normal engine operation while illuminating the malfunction light. When the engine malfunction light illuminates, follow these steps: First check if the engine operates normally. If there's shaking, black smoke, etc., avoid restarting. Never restart if the red warning light is on. If the engine starts, turn it off for 5-10 minutes. Then without pressing brakes (or clutch for manual transmissions), activate the ignition to ON position to initiate self-diagnosis. After 5-10 seconds, check if the light turns off. If the light remains on, visit a service center immediately. Technicians can use diagnostic tools to read trouble codes and perform targeted repairs.
