What Causes the Engine Malfunction Light to Stay On in a Vehicle?

[Pires]

There are primarily 7 reasons why the engine malfunction light stays on: Sensor failure: 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 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 the air-fuel mixture: Poor combustion can lead to engine carbon deposits 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, or fuel line blockage can all cause poor combustion of the air-fuel mixture. Turbocharging issues: The intake boost pipe or turbocharger can also trigger the engine malfunction light. The most common issue is turbocharger damage, accompanied by symptoms such as oil leaks, excessive oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust. Intake issues: If the vehicle's intake system has problems, it may cause engine pipe blockages, and in severe cases, trigger the malfunction light. A dirty air filter that is not cleaned regularly can lead to intake issues. Exhaust issues: Exhaust system failures can also trigger the engine malfunction light. Common causes include rear oxygen sensor failure, catalytic converter failure, exhaust camshaft and bearing failure, with the catalytic converter being the most frequent issue. Using leaded gasoline, lead or silicon-based lubricant additives, physical damage to the catalytic converter, or fuel system failures can easily cause catalytic converter problems. Anti-theft system failure: If the vehicle's electronic anti-theft system malfunctions or the anti-theft controller does not match the engine electronic controller, the anti-theft system can prevent the engine from operating normally and trigger the malfunction light. If the engine malfunction light stays on, follow these steps: First, check if the engine is running normally, such as whether there is 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 for 5-10 minutes, then press the start button without stepping on the brake pedal, or turn the key halfway to the 'on' position without depressing the clutch. The vehicle will perform a self-check after powering on. Wait 5-10 seconds to see if the malfunction light turns off. If the light remains on, visit a service center as soon as possible. The service center can use a portable diagnostic tool to read the fault code, identify the issue, and perform targeted repairs.

[DeJace]

I've encountered the engine warning light staying on several times. Last time it happened when I was driving my friend's old car, and I had to pull over immediately to check. The most common cause is a faulty sensor, like the oxygen sensor monitoring the exhaust pipe - if it gets dirty or malfunctions, the engine triggers an alarm. Another possibility is a clogged exhaust pipe affecting the emission system. It could also be spark plug ignition issues causing engine misfires and triggering the light. Don't underestimate this warning light - prolonged neglect may lead to engine overheating or fuel wastage, doubling repair costs. I suggest using an OBD scanner to read the trouble codes first to identify the specific issue before taking action. If all else fails, take it to a repair shop immediately - safety comes first.