P0031

P0031 - HO2S Heater Circuit Low (B1/S1)






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
After the Heater is on from Off, the voltage after 5msec is less than threshold value, the ECM determines that a fault exists and a DTC is stored.


Detecting Condition and Specifications





Wiring Schematic





Signal Waveform