Air-Fuel Ratio Oxygen Sensor 234-4296/234-4309 OS2140 Universal for Multiple Vehicle Models

Air-fuel ratio oxygen sensor monitors exhaust oxygen content and feeds ECU to adjust injection; OEM OS2140; fits Nissan and Infiniti models (e.g., 22690-2A000). Installation difficulty moderate; common faults include carbon buildup or aging causing higher fuel consumption; disconnect negative battery before replacing.