The engine warning light may illuminate during power-on self-test or under other conditions. The power-on self-test is an indication that the vehicle is monitoring the status of all sensors before driving. Generally, if the engine is not started after power-on, the light will turn off by itself after about 3 seconds. In other cases, if the EPC indicator light remains illuminated for an extended period after the vehicle is started, the main causes may include faults in the engine intake system, throttle valve, fuel system, engine itself, ECU control unit, or brake lights. Below is a detailed explanation of each potential issue: Sensor Problems: Sensors include those for coolant temperature, crankshaft position, air flow, intake temperature, oxygen levels, etc. When these sensors are damaged, have poor connections, or experience signal interruptions, the vehicle's ECU cannot accurately obtain engine data, which may trigger the engine warning light. Solution: If such issues occur, promptly visit a repair center for professional inspection to eliminate potential safety hazards. Maintenance Issues: Poor engine maintenance is one of the most common reasons for the engine warning light to illuminate. Vehicles have specific maintenance cycles, and failure to adhere to these cycles, combined with poor driving habits, can increase the burden on the engine, eventually triggering the warning light. Solution: Follow the maintenance schedule in your vehicle's manual, ensuring timely and comprehensive maintenance to prevent non-maintenance-related issues. Fuel and Oil Quality Issues: Fuel and oil quality can affect engine performance. Vehicles typically require specific fuel grades and types of oil (semi-synthetic or full synthetic). If the wrong fuel or oil is used over time, it can cause engine wear and trigger the warning light. Solution: Always use the recommended fuel grade and appropriate engine oil for your vehicle. Poor Combustion of Air-Fuel Mixture: Faulty spark plugs, fuel pump issues, or clogged fuel lines can lead to poor combustion of the air-fuel mixture. This can cause carbon buildup or engine knocking, which the oxygen sensors detect and report to the ECU, triggering the warning light. Solution: Inspect the engine's ignition coils and spark plugs. Check the performance of related sensors, such as oxygen sensors (front and rear), coolant temperature sensor, intake temperature sensor, throttle position sensor, air flow meter, and intake manifold pressure sensor. Examine the air filter for contamination—if clogged, it can cause an overly rich mixture and should be cleaned or replaced as needed. Also, check for fuel injector leaks and the performance of the fuel pressure regulator. Intake Issues: Proper air intake is crucial for combustion. A dirty or clogged air filter can restrict airflow, leading to engine performance issues and eventually triggering the warning light. Solution: Regularly clean or replace the air filter to ensure the intake system functions properly. Turbocharger Issues: Problems with the intake boost system or turbocharger can also trigger the engine warning light. Common issues include turbocharger failure, accompanied by symptoms like oil leaks, excessive oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust. Solution: Visit a 4S shop to inspect and replace the turbocharger. In most cases, repair is not cost-effective, and replacement is recommended. Exhaust System Issues: Faults in the rear oxygen sensor, catalytic converter, or exhaust camshaft and bearings can trigger the warning light. The most common issue is a faulty catalytic converter, which can be caused by physical damage or fuel system problems. Solution: Use lead- or silicon-based lubricants to maintain and clean the catalytic converter. Anti-Theft System Issues: If the vehicle's anti-theft system malfunctions or the anti-theft controller does not match the engine ECU, the engine may not operate correctly, and the warning light may illuminate. Solution: Seek professional help at a repair shop, as this issue cannot be resolved independently. Engine Misfire: If one or more cylinders fail to function properly, the engine may experience power loss, difficulty starting, or unstable idling. Solution: Identify the faulty cylinder and replace damaged components. If internal mechanical damage is present, major repairs may be required.
