P0137 Code: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

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The P0137 is a generic OBD-II Diagnostic Trouble Code (DTC) indicating that the Engine Control Module (ECM/PCM) has detected a consistently low voltage signal from the oxygen sensor located after the catalytic converter on Bank 1 (Sensor 2). This sensor monitors catalytic converter efficiency and helps ensure proper exhaust emissions.

Quick Summary
Code: P0137
Description: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
System: Fuel & Air Metering
Severity: Moderate
Safe to Drive? Yes, but repair is recommended soon.

Fault Code Description

When the downstream oxygen sensor voltage stays below approximately 0.1 volts for longer than the manufacturer allows, the ECM stores code P0137 and may illuminate the Check Engine Light. Since this is a downstream sensor, the fault mainly affects emissions monitoring rather than fuel control.

Meaning of the Code

The ECM expects the Bank 1 Sensor 2 oxygen sensor to produce a changing voltage based on oxygen content in the exhaust gases. If the voltage remains unusually low, the computer assumes there is an electrical fault, exhaust leak, sensor failure, or extremely lean exhaust condition.

Vehicles Commonly Affected

  • Ford
  • Chevrolet / GMC
  • Toyota
  • Honda
  • Nissan
  • Hyundai / Kia
  • Dodge / Chrysler / Jeep
  • BMW
  • Volkswagen
  • Most OBD-II vehicles (1996+)

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