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 PCM monitors this signal and determines whether the air/fuel mixture is rich or lean. The PCM 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 HO2S tip temperature and signal at the same time to check open circuit of Pumping Current Circuit. The PCM sets DTC P2237 if front O2 tip temperature is higher than the predetermined threshold and front HO2S signal stuck is detected. If the same error code is set in the next driving cycle, the ECM illuminates the MIL.

DTC Detecting Condition





Schematic Diagram





Signal Waveform

1. Voltage in HO2S

Test Condition : Ignition ON, Engine OFF / HO2S disconnected





2. Scan Tool Data




Fig 1) Normal HO2S (B1S1) value with engine warm-up and idling : Approx. 1.5 - 2.0V
>Signal decreases with rich air/fuel mixture and increases with lean air/fuel mixture
>Fuel cut-off mode : Approx 3.2V