P0137 OBD-II Trouble Code: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)

Check Engine Light

P0137 code definition

O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)

What the P0137 code means

P0137 is the OBD-II generic code indicating the O2 sensor for bank 1 sensor 2 is failing to increase the voltage output above .21 volts indicating excessive oxygen in the exhaust.

This code occurs when the engine control module (ECM) sees the voltage of the O2 sensor for bank 1 sensor 2 below .21 volts when the ECM has commanded the fuel to a targeted rich condition on that bank of the engine.

What causes the P0137 code?

  • The ECM detects the low voltage problem and turns on the Check Engine Light.

  • The ECM uses other O2 sensors to try and control the fuel injection with their values.

  • Exhaust leaks

What are the symptoms of the P0137 code?

  • The engine will run rich during the testing of the sensor for problems.
  • The Check Engine Light will be illuminated.
  • You may have exhaust leaks before or near the O2 sensor in question.

How does a mechanic diagnose the P0137 code?

  • Scans codes and documents freeze frame data then clears codes to verify failure.

  • Monitors O2 sensor data to see if the voltage is switching back and forth between low and high at a fast rate compared to other sensors.

  • Checks the O2 sensor wiring and the harness connections for any corrosion in the connections.

  • Checks the O2 sensor for any physical damage or fluid contamination.

  • Checks for exhaust leaks before the sensor.

  • Follows the manufacturer's specific pinpoint tests for further diagnosis.

Common mistakes when diagnosing the P0137 code?

Follow these simple guidelines to prevent misdiagnosis:

  • Repair any exhaust leaks before the sensor to prevent excess oxygen getting into the exhaust stream causing the low voltage readings.

  • Check the O2 sensor for oil or coolant contaminants that could foul the sensor.

  • Repair any harness that is damaged properly to prevent erratic readings from the sensors.

  • Check the removed O2 sensor for damage from a broken catalyst and replace the catalyst if it has come apart.

How serious is the P0137 code?

  • The voltage output from the O2 sensor may be due to exhaust leaks causing the O2 sensors to give low output voltages.

  • The ECM cannot correctly control the fuel-to-air ratio of the engine fuel mixture if any O2 sensor is malfunctioning. This leads to poor fuel mileage and possible premature failure for some engine components.

What repairs can fix the P0137 code?

Additional comments for consideration regarding the P0137 code

The O2 sensor circuit for bank 1 sensor 2 is used to give a voltage feedback to the ECM showing how much oxygen is in the exhaust stream to help the engine control the fuel-to-air ratio better. The low voltage condition is excessive oxygen in the exhaust or problems causing the issue.

Need help with a P0137 code?

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