Which component monitors the operating efficiency of a catalytic converter?

The component that monitors the operating efficiency of a catalytic converter is the oxygen (O2) sensor. This sensor plays a crucial role in assessing whether the catalytic converter is functioning properly by measuring the level of oxygen in the exhaust gases.

When the catalytic converter operates correctly, it converts harmful exhaust gases into less harmful emissions. The O2 sensor is located before and after the catalytic converter—these two sensors provide the engine control module (ECM) with data about the oxygen levels in the exhaust. By comparing the readings from these sensors, the ECM can determine if the catalytic converter is efficiently converting the exhaust gases. If the readings indicate a significant discrepancy, it may signal that the converter is failing or not operating as intended, allowing for diagnostic actions to be taken.

The other components listed do not serve this specific purpose. The mass airflow sensor primarily measures the amount of air entering the engine to help optimize fuel injection. The throttle position sensor provides data on the position of the throttle plate to aid in engine management. The engine temperature sensor monitors the engine's operating temperature for efficient performance. While these components are essential for overall engine management, none directly monitor the efficiency of the catalytic converter like the O2 sensor does.