The three-way catalytic converter's low efficiency or damage can lead to exhaust system malfunctions, incomplete exhaust purification, and subsequently trigger the engine malfunction light. The specific principles are as follows: When engine exhaust passes through the exhaust pipe, the catalytic action of the purifying agent in the three-way catalytic converter enhances the activity of CO, HC, and NOx, facilitating oxidation-reduction reactions. Here, CO oxidizes into colorless, non-toxic CO₂ at high temperatures, HC compounds oxidize into H₂O and CO₂, and NOx reduces to N₂ (nitrogen) and O₂ (oxygen), thereby purifying the engine's exhaust emissions. If the three-way catalytic converter's efficiency is too low, exhaust purification becomes incomplete, causing the engine malfunction light to illuminate. In such cases, cleaning the three-way catalytic converter is recommended. If the warning persists after cleaning, replacement of the three-way catalytic converter is necessary. Apart from exhaust issues caused by low three-way catalytic converter efficiency, there are six other reasons for the engine malfunction light to illuminate: Sensor Malfunction: Sensors such as coolant temperature, crankshaft position, air flow, intake air temperature, and oxygen sensors, when damaged, poorly connected, or interrupted, prevent the vehicle's ECU from accurately obtaining engine data, triggering the engine malfunction light. Fuel Quality Issues: Failure to use the fuel and engine oil as specified by the manufacturer may cause engine wear, leading to the malfunction light illuminating. Poor Combustion of Air-Fuel Mixture: Incomplete combustion can result in engine carbon deposits or knocking. Detected by the oxygen sensor and reported to the ECU, the malfunction light activates as a warning. Spark plug failure, ignition coil failure, fuel pump failure, and fuel line blockages can all cause poor combustion of the air-fuel mixture. Turbocharging Issues: Intake boost pipes and turbochargers 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, and blue or black smoke from the exhaust. Exhaust System Issues: Exhaust faults can also cause the engine malfunction light to illuminate. Common causes include rear oxygen sensor failure, three-way catalytic converter failure, exhaust camshaft and bearing faults, with the three-way catalytic converter being the most frequent culprit. Use of leaded gasoline, lead or silicon-containing lubricant additives, physical damage to the catalytic converter, and fuel supply system failures can all lead to three-way catalytic converter issues. Anti-Theft System Malfunction: If the vehicle's electronic anti-theft system fails or the anti-theft controller does not match the engine electronic controller, the anti-theft system can prevent the engine from operating normally, simultaneously illuminating the engine malfunction light.
