Which system is used to monitor the effectiveness of the catalytic converter?

The O2 sensor plays a critical role in monitoring the effectiveness of the catalytic converter. By measuring the amount of oxygen in the exhaust gases before and after they pass through the catalytic converter, the O2 sensor provides essential data on the converter's performance. If the catalytic converter is functioning properly, the O2 levels should stabilize within a certain range, indicating effective conversion of harmful emissions.

When the sensor detects a significant difference in oxygen levels between the upstream and downstream of the converter, it signals a potential failure or inefficiency in the catalytic converter, which could lead to increased emissions and trigger a diagnostic trouble code. This monitoring helps ensure that vehicles meet environmental standards and operate efficiently.

The other systems mentioned, such as the MAF sensor, EGR system, and fuel injector system, perform different functions related to air-fuel mixture and emissions control but do not specifically monitor catalytic converter performance like the O2 sensor does.