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 control unit of the linear oxygen sensor built inside the ECM monitors short circuit error on all front Heated Oxygen Sensor (HO2S) control lines (PIN#19, PIN#40, PIN#41 and PIN#53) and ECM sets P0131 with short circuit to ground. If same code is set again in the next driving cycle, MIL is illuminated.

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