Code Definition

P0157 — Oxygen Sensor Circuit Low Voltage (Bank 2 Sensor 2)

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

About P0157

P0157 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 P0157 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 P0157 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 P0157 code is set when the Engine Control Module (ECM) detects that the voltage from the Bank 2, Sensor 2 oxygen sensor stays lower than expected, typically below about 0.4 volts for more than around twenty seconds. This is the downstream sensor mounted after the catalytic converter on the cylinder bank that does not contain cylinder number 1. A persistently low signal indicates high oxygen content in the exhaust, which can be caused by a genuine lean condition, an exhaust leak drawing in outside air near the sensor, a sensor biased low, or a circuit fault such as a short to ground or an o...

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