P2271 Subaru HO2S Signal Stuck Rich Bank 1 Sensor 2

Possible causes

– Faulty Rear Heated Oxygen Sensor Bank 1
– Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
– Intake air leaks
– Exhaust gas leaks
– Inappropriate fuel pressure
– Faulty fuel injectors

What about the obd code?

The Powertrain Control Module (PCM) detected the HO2S12 sensor has reported a rich condition for an extended period during an intrusive test

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– High Fuel Consumption
– Excessive Smoke from Exhaust

P2271 Subaru Description

The Powertrain Control Module (PCM) supplies a voltage of about 450 mV between the HO2S high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the heated oxygen sensor (HO2S) voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if majority of the samples are out of the operating range.