What does Bank 2 O2 sensor 1 and 2 mean on a 2002 Mitsubishi Diamante?

The Bank 2 O2 sensors on a 2002 Mitsubishi Diamante refer to the oxygen sensors located on the side of the engine that does not contain the #1 cylinder, typically the passenger side. Sensor 1 is the upstream O2 sensor that monitors the air-fuel mixture before it enters the catalytic converter, while Sensor 2 is the downstream sensor that checks the efficiency of the catalytic converter after the exhaust gases have passed through it. Issues with these sensors can trigger the check engine light and affect engine performance and emissions.