General Information

P0031 HO2S Heater Control Circuit Low (Bank 1 / Sensor 1)

General Information

Component Location





General Description

In order to control emissions of the CO, HC and NOx components of the exhaust gas, heated oxygen sensor (HO2S), mounted on the front side and rear side of catalytic converter, detects the oxygen content in the exhaust gas. The front HO2S signal is used to control air/fuel ratio (closed loop fuel control) and the rear HO2S signal is used to monitor front HO2S and catalyst for proper operation.
The HO2S requires a minimum temperature to operate properly and provide a closed loop fuel control system. The HO2S contains the heater element to reduce its warming-up time and ensure its performance during all driving conditions. The ECM controls this heater element by duty cycle.
The main relay supplies voltage to the heater and the ECM provides a ground circuit for activating the heater.

DTC Description

When ECM detects short to ground in the heater control circuit (S1), ECM sets DTC P0031.

DTC Detecting Condition





** S1 : upstream oxygen sensor / S2 : downstream oxygen sensor

Specification





Diagnostic Circuit Diagram





Signal Waveform & Data




The HO2S requires a minimum temperature to provide a closed loop fuel control system. So the HO2S contains a heater element to reduce its warm-up time and ensure its performance during all driving conditions. The HO2S heater is controlled ON after engine start except for Cold condition and high speed acceleration. The ECM controls this heater element by duty cycle. The main relay supplies voltage to the heater and the ECM provides a ground circuit for activating the heater.