Will the malfunction indicator light come on if the three-way catalyst is missing?
3 Answers
Missing the three-way catalyst will cause the malfunction indicator light to illuminate. Simply adding the three-way catalyst can resolve the issue. Impact of missing the three-way catalyst: The engine emission warning light on the instrument cluster will turn on, and the vehicle's exhaust emissions will significantly exceed standards. Driving on the road may result in traffic violations being captured by cameras, leading to fines and other penalties. If the vehicle reaches its annual inspection period, it will definitely fail the inspection. The three-way catalytic converter is installed between the engine exhaust manifold and the muffler. It converts harmful gases such as CO, CH, and NOx produced by engine combustion into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions on the ceramic and precious metal mesh structure inside the catalytic converter. Because this converter can simultaneously transform three major harmful substances in the exhaust into harmless substances, it is called a three-way catalytic converter. Failure of the three-way catalytic converter is more common in older vehicle models and luxury cars that are overly sensitive to fuel quality. The damage to the three-way catalytic converter is related to its own quality and the vehicle's usage. Vehicles that are rarely used, left unused for long periods, or driven continuously at low speeds are more prone to issues with the three-way catalytic converter. For example, vehicles that do not travel long distances or are usually driven at only 30 to 40 km/h are more likely to develop carbon deposits.
I previously studied automotive electronic systems and know that the check engine light will definitely come on if the catalytic converter is missing. Because the vehicle's engine control unit constantly monitors the catalytic converter's efficiency using oxygen sensors. The catalytic converter is responsible for converting harmful gases like carbon monoxide and hydrocarbons in the exhaust. Once it fails or is missing, the sensor data will become abnormal, and the ECU will immediately trigger an error code and illuminate the warning light. I've driven several older cars and encountered this issue. At first, I thought it was a minor problem, but delaying repairs led to a significant increase in fuel consumption and even resulted in fines for excessive emissions. Modern car designs are more sophisticated, with sensors providing alerts at the slightest irregularity—don't ignore them. I recommend visiting a repair shop early to read the fault codes. It might not just be a catalytic converter issue; sensor or wiring problems are also common. Safety first, after all.
As a car owner who frequently deals with repairs, my experience tells me that the check engine light will definitely come on if the catalytic converter is missing. Last time my car's converter got clogged to the point of failure, the exhaust sound changed under the car, and the check engine light started flashing. The ECU compares the conversion efficiency of the catalytic converter using the front and rear oxygen sensors. When it fails, the data discrepancy becomes large enough to trigger the light. Not addressing it promptly can have serious consequences: the engine may run unevenly, fuel consumption increases, and you might even fail the annual inspection. After I replaced the catalytic converter, the light went off, and the car ran smoothly again. For beginners, I recommend not attempting to remove it yourself—just take it to a reputable shop for a diagnostic check. Small issues can be fixed quickly and hassle-free.
