P2243 Audi Oxygen (O2) Sensor Reference Voltage Circuit / Open (Bank 1 – Sensor 1)

The linear O2 sensor is mounted on the front side of the Catalytic Converter (warm-up catalytic converter) or in the front exhaust pipe. It detects a wide range of air/fuel ratios in the exhaust gas from the rich to lean regions. This linear O2 sensor produces a current that corresponds to a specific air/fuel ratio. The Engine Control Module (ECM) monitors this signal and determines whether the air/fuel mixture is rich or lean. The ECM constantly monitors the linear O2 sensor and increases or decreases the fuel injection duration using this signal. This is called closed-loop fuel control operation.