P2251 Code: Meaning, Causes, and Symptoms | OBD2 Codes

P2251 – O2 Sensor Negative Current Control Circuit Open Bank 1 Sensor 1


P2251: DIY Repairing Video Tutorial


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P2251 Possible Symptoms

  Engine Light ON (or Service Engine Soon Warning Light)  

P2251 Possible Causes

  Faulty Front Oxygen Sensor Bank 1,Front Oxygen Sensor Bank 1 harness is open or shorted,Front Oxygen Sensor Bank 1 circuit poor electrical connection  

P2251 Description

  The Front Oxygen Sensor (O2 Sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.