Code Definition

P0131 — O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

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

About P0131

P0131 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 P0131 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 P0131 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 P0131 fault code is set when the Engine Control Module (ECM) detects a lower than expected voltage output from the oxygen sensor in Bank 1, Sensor 1. This sensor is typically located before the catalytic converter (upstream) in the exhaust system. Low voltage output from this sensor can indicate that the oxygen level in the exhaust is higher than expected, which could be due to a lean air-fuel mixture or a malfunctioning sensor. The ECM uses this sensor's data to regulate the air-fuel ratio. A low voltage signal could be caused by issues in the sensor itself, wiring problems, or exhaust le...

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