Why does the Mercedes-Benz engine malfunction indicator light come on while the car can still run normally?

[DelAriel]

The engine malfunction indicator light coming on may be a warning, indicating that certain system parameters of the car may have exceeded the set range. In this case, the car can usually continue to drive, and the light is generally yellow. There is also a more serious situation where the light turns red, indicating a very severe fault. Although the car may still be able to drive, for safety reasons, it must be stopped immediately, the engine turned off, and further driving prohibited. The fault must then be checked. There are mainly seven reasons for the engine malfunction indicator light to come on: Sensor failure: The sensors referred to here include those for coolant temperature, crankshaft position, air flow, intake air temperature, oxygen sensors, etc. When these sensors are damaged, have poor contact, or signal interruption, the car's ECU cannot accurately obtain engine data, causing the engine malfunction indicator light to come on. Fuel or oil quality issues: If fuel or engine oil is not added as required by the manufacturer, it may cause engine wear, leading to the malfunction light coming on. Poor mixture combustion: Poor mixture combustion can cause engine carbon buildup or knocking. When detected by the oxygen sensor and reported to the ECU, the malfunction light will come on as a warning. Faulty spark plugs, ignition coils, fuel pumps, or clogged fuel lines can all lead to poor mixture combustion in the engine. Turbocharging issues: Intake turbocharging pipes and the turbocharger can also cause the engine malfunction light to come on. The most common issue is turbocharger damage, accompanied by symptoms such as oil leaks, high oil consumption, reduced power, metallic noises, or blue or black smoke from the exhaust pipe. Intake issues: If there is a problem with the car's intake, it may lead to engine pipe blockage, and in severe cases, cause the engine malfunction light to come on. A dirty air filter that is not regularly cleaned can lead to intake problems. Exhaust issues: Exhaust faults can also cause the engine malfunction light to come on. The rear oxygen sensor, three-way catalytic converter, exhaust camshaft, and bearing faults are all causes of exhaust problems, with the three-way catalytic converter being the most common. Using leaded gasoline, lead or silicon-containing lubricant additives, physical damage to the three-way catalytic converter, or 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 malfunctions, or if the anti-theft controller does not match the engine electronic controller, the anti-theft system can cause the engine to malfunction, and the engine malfunction light will come on. If the engine malfunction light comes on, follow these steps: First, check if the engine is running normally and whether there are issues such as shaking or smoke. If so, try not to restart the engine. Especially, do not restart the engine if the light is red. If the engine can start, 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 to see if the malfunction light on the dashboard turns off. If the malfunction light does not turn off, visit a service station as soon as possible to find the cause. The service station can use a portable diagnostic tool to read the fault codes, obtain fault information, and perform targeted repairs.