P2237 Subaru Oxygen (O2) Sensor Positive Current Control Circuit / Open (Bank 1 – Sensor 1)

Possible causes

– Faulty Heated Oxygen Sensor Bank 1 Sensor 1
– Heated Oxygen Sensor Bank 1 Sensor 1 harness is open or shorted
– Heated Oxygen Sensor Bank 1 Sensor 1 circuit poor electrical connection

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P2237 Subaru Description

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.