Code Definition

P0031 (28) — Oxygen Sensor Heater 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

The P0031 code indicates a low voltage issue in the heater control circuit of the upstream oxygen sensor (Bank 1 Sensor 1). This sensor is located before the catalytic converter. The heater element in the oxygen sensor is critical for bringing the sensor to its operating temperature swiftly after engine start. The Engine Control Module (ECM) sets this code when it detects a lower than expected voltage in the heater circuit, which could impair the sensor's ability to accurately assess the air fuel mixture.

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