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P0139 - OBD-II Trouble Code

Our automotive experts have put together the following information about the P0139 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P0139 code.

OBD II Fault Code

  • OBD II P0139

Fault Code Definition

When the up and down "cross-counting" voltage activity from the Oxygen Sensor is too slow, code P0139 is triggered and the Check Engine/Service Engine Soon Light will illuminate.

P0139 Symptoms

  • Check Engine Light will illuminate
  • In many cases, no abnormal symptoms may be noticed
  • In some cases, the vehicle will fail an Emissions Test
  • In some cases, the engine may "ping" and produce excess NOx 

Common Problems That Trigger the P0139 Code

  • Defective Catalytic Converter
  • Faulty Rear Oxygen Sensor wiring or connections

Common Misdiagnoses

  • Oxygen Sensor Sensor is replaced when the problem is a defective Catalytic Converter
  • Oxygen Sensor is replaced when the problem is faulty sensor wiring or connections
  • Oxygen Sensor is replaced when the problem is an exhaust leak in front of the Oxygen Sensor

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