Will the malfunction indicator light up if the three-way catalyst is missing?
3 Answers
The absence of the three-way catalyst will cause the malfunction indicator to light up. The three-way catalytic converter is the most important external purification device installed in the vehicle's exhaust system. How to determine the condition of the three-way catalytic converter: Visual inspection. Observe the exterior of the three-way catalytic converter for any damage or stains. If there are scratches, cracks, etc. on the surface, it is likely that the three-way catalytic converter has been damaged. If there are obvious gray spots in the center of the catalytic converter protective cover, severe discoloration spots, or purple stains on the shell, the three-way catalytic converter may have experienced overheating issues. Check the engine exhaust condition. Place your hand near the exhaust pipe outlet to feel the exhaust flow and check if the three-way catalytic converter is clogged or has poor exhaust flow. Another method is to open the air filter, remove the filter element, and observe if there is exhaust backflow during rapid acceleration, indicating poor engine exhaust flow. To check the condition of the TWC (Three-Way Catalyst), also inspect if the secondary air injection pump is functioning properly. Use an infrared thermometer to determine. Compare the temperature difference before and after the TWC using an infrared thermometer. If the temperature difference between the inlet and outlet of the three-way catalytic converter is less than 10°C, the TWC is already damaged.
I once encountered this situation where the car was driving normally, but the check engine light suddenly came on, which made me a bit worried. After getting it checked, I found out that the catalytic converter had been stolen because that part is worth some money. The mechanic told me that without it, the engine's emission data would be abnormal, and the onboard computer automatically detects the excess and lights up the check engine light to alert the owner about an emission system issue. Later, I spent some money to replace the catalytic converter, the light went off, and the car passed the annual inspection without any problems. Actually, vehicle safety is very important—don't underestimate this light; it can help avoid bigger losses like fines or more serious pollution.
Having repaired cars for many years, I've seen numerous cases where the catalytic converter fails or is removed. In such situations, the check engine light will definitely come on because the vehicle's OBD system continuously monitors exhaust emissions. Once the catalytic converter is gone, the readings from the front and rear oxygen sensors won't match, causing the ECU to detect a problem and illuminate the warning light. If not addressed promptly, the engine may enter a protective mode, leading to increased fuel consumption and reduced power. Additionally, the vehicle will certainly fail the emissions test during annual inspections. Therefore, car owners should never remove this critical component just to save a little money or gain a slight horsepower boost.
