Auto Systems and Repair: P0139 - OBD-II Trouble 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.

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