Code Definition

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

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0031

P0031 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0031 is stored, the module has detected a signal or supply voltage lower than the expected operating range; a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0031 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

DTC P0031 sets when the Engine Control Module detects a low voltage or high current condition in the heater control circuit of the upstream oxygen sensor on bank 1 sensor 1, the sensor located ahead of the catalytic converter. The heater element brings the sensor to operating temperature within seconds of start up so closed loop fuel control can begin quickly, and the ECM controls it through a low side driver while monitoring the circuit. The Low code specifically points to the control circuit being pulled low, most often a short to ground in the heater wiring, a heater element that has shorte...

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