General Information

Component Location





General 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 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.

DTC Description

The ECM monitors front O2 sensor signal level during fuel cut-off operation. This signal monitoring will determine open circuit of Reference Ground Circuit (ECM pin No. 46). The ECM sets DTC P2251 if front O2 signal during fuel cut-off is higher than predetermined threshold.
If the same error code is set in the next driving cycle, the ECM illuminates the MIL.

DTC Detecting Condition





Schematic Diagram





Signal Waveform