Toyota Vios NCP42 Yaris Air-Fuel Ratio Sensor 89465-52050 Rear Oxygen Sensor

When your Toyota Vios NCP42 or Yaris shows idle instability, clearly rising fuel consumption, exhaust odor, and engine warning light (codes such as P0136 or P0141), the rear oxygen sensor (air-fuel sensor) has aged and failed. It normally sends feedback to the ECU about residual oxygen in exhaust to adjust fuel injection for optimal air-fuel ratio, improving fuel economy and reducing emissions. OEM numbers 89465-20860/89465-52050; compatible with Toyota Vios NCP42 and Yaris. Installation must be performed cold; disconnect battery negative before disassembly; handle sensor wiring carefully to avoid damage; use a dedicated socket to tighten to specified torque to prevent overtightening.