Why Does the Engine Warning Light Illuminate When the Three-Way Catalytic Converter Efficiency Is Too Low?

[VanBrianna]

The three-way catalytic converter's efficiency being too low or damaged can lead to exhaust system malfunctions, incomplete exhaust purification, and subsequently cause the engine warning light to illuminate. The specific principle is as follows: When engine exhaust gases pass through the exhaust pipe, due to the catalytic action of the purifying agents in the three-way catalytic converter, the activity of CO, HC, and NOx is enhanced, facilitating oxidation-reduction reactions. CO is oxidized into colorless, non-toxic CO₂ at high temperatures, HC compounds are oxidized into H₂O and CO₂, and NOx is reduced into 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, and the engine warning light will illuminate. At this point, cleaning the three-way catalytic converter should be considered. If the warning persists after cleaning, the three-way catalytic converter needs to be replaced. Apart from exhaust issues caused by low efficiency of the three-way catalytic converter, there are six other reasons why the engine warning light may illuminate: Sensor Malfunction: Sensors such as coolant temperature, crankshaft position, air flow, intake temperature, and oxygen sensors, when damaged, poorly connected, or experiencing signal interruptions, prevent the car's ECU from accurately obtaining engine data, leading to the engine warning light illuminating. Fuel Quality Issues: Failure to add fuel and engine oil as required by the manufacturer may cause engine wear, triggering the warning light. Poor Combustion of Air-Fuel Mixture: Poor combustion can lead to engine carbon deposits or knocking, detected by the oxygen sensor and reported to the ECU, which then illuminates the warning light. Issues like spark plug failure, ignition coil failure, fuel pump failure, or fuel line blockage can cause poor combustion of the air-fuel mixture. Turbocharging Problems: Intake boost pipes and turbochargers can also cause the engine warning light to illuminate. The most common issue is turbocharger damage, accompanied by symptoms like oil leaks, excessive oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust. Exhaust System Issues: Exhaust malfunctions can also trigger the engine warning light. Causes include rear oxygen sensor failure, three-way catalytic converter issues, exhaust camshaft and bearing failures, with the three-way catalytic converter being the most common culprit. Using leaded gasoline, lead- or silicon-based lubricant additives, physical damage to the catalytic converter, or engine fuel supply system failures can easily lead to three-way catalytic converter problems. Anti-Theft System Malfunction: If the car's electronic anti-theft system malfunctions or the anti-theft controller is incompatible with the engine electronic controller, the anti-theft system can prevent the engine from operating normally, and the engine warning light will illuminate.