P0139: Oxygen Sensor Circuit Slow Response (Bank1, Sensor2)

What Does The P0139 Code Mean?

This involves the rear oxygen sensor on the driver’s side. This code indicates the engine air fuel ratio is not being adjusted by the oxygen sensor signal or the ECM as expected to do so, or not adjusted as often as expected to do so once the engine is warmed or under normal engine use. Bank 1 is the is the bank of cylinders that contains cylinder #1.

What Are The Symptoms Of The P0139 Code?

You will likely not notice any drivability problems, although there may be symptoms.

What Are The Potential Causes Of The P0139 Code?

A code P0139 may mean that one or more of the following has happened:

• The oxygen sensor is faulty
• The wiring to the sensor is broken / frayed
• There is an exhaust leak

How Can You Fix The P0139 Code?

The simplest thing to do is to reset the code and see if it comes back.

If the code comes back, the problem is more than likely the rear driver’s side oxygen sensor. You will likely wind up replacing it but you should also consider these possible solutions:

• Check and fix any exhaust leaks
• Check for wiring problems (shorted, frayed wires)
• Check the frequency and amplitude of the oxygen sensor (advanced)
• Check for a deteriorating / contaminated oxygen sensor, replace if necessary
• Check for inlet air leaks
• Check the MAF sensor for proper operation

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> O2 Sensor
>>> Twippo 372Pcs Waterproof Wire Connectors Kit
>>> INNOVA 5210

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Check This Video For Reference

Reference Sources

Diagnostic Trouble Code (DTC) Charts and Descriptions for P0139 – Page 36.