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P2251 - O2 Sensor Negative Current Control Circuit/Open Bank 1 Sensor 1

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Possible causes
- Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 harness is open or shorted
- Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1 circuit poor electrical connection
- Faulty Rear Air/Fuel Ratio Sensor Bank 1 Sensor 1
Help with this
- Engine Light ON (or Service Engine Soon Warning Light)
P2251 Description
The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) is installed in the exhaust manifold and detects oxygen content in the exhaust gas. The rear A/F sensor transmits a signal to the powertrain control module (PCM), and it enables overall feedback control. The PCM controls fuel injection duration by comparing the target air/fuel ratio with the rear A/F sensor signal. When the VSB1 terminal voltage is more than a specified value for a predetermined time, the PCM detects a malfunction and stores a DTC.
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Engine Light ON?

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