Kia Spectra 2005 2.0L Automatic - P2251 Error After Replacing Upper O2 Sensor
My Kia Spectra 2005 with a 2.0L automatic transmission originally showed error code P0171, which I resolved by replacing the upper pre-catalyst oxygen sensor. However, after the replacement, I am now receiving error code P2251 — indicating a lean condition detected by the Powertrain Control Module (PCM). The generic description for this code is 'negative current' or 'circuit open'. I have inspected all connectors and they appear to be secure and properly connected. I'm concerned whether I may have installed a faulty aftermarket sensor instead of an OEM part. Could the issue stem from using a non-OEM sensor? Any guidance on diagnosing this would be greatly appreciated.
Code P2251 does not indicate that an oxygen sensor needs replacement — it signals a lean air-fuel mixture being detected by the PCM. This suggests a fuel delivery or intake issue, not necessarily a faulty sensor. I suspect your replaced O2 sensor may have been aftermarket rather than original Kia equipment. If this is true, that could explain why the code reappeared. To confirm, please verify the part number and source of the sensor. A wiring diagram and voltage readings using a multimeter will be essential for further diagnosis. For more details, refer to: http://www.obd-codes.com/p0171