What does the term “O2 sensors” refer to in an emissions context?

The term "O2 sensors" in an emissions context specifically refers to sensors that measure the amount of oxygen in exhaust gases. These sensors play a crucial role in the vehicle's emissions control system by providing real-time feedback to the engine control unit (ECU). They help monitor the air-fuel mixture entering the engine by determining how much oxygen exists in the exhaust. This information allows the ECU to adjust fuel injection accordingly, ensuring optimal combustion and reducing harmful emissions.

Oxygen sensors are vital for maintaining compliance with environmental regulations and improving fuel efficiency. They are typically placed in the exhaust system, before and after the catalytic converter, to assess the converter's performance. Proper functioning of these sensors contributes significantly to the overall effectiveness of the vehicle’s emissions control system.