Air & Fuel Mixture ControlOBD2 Codes

P0156 – Meaning, Causes, Symptoms, & Fixes

Reading Time: 2 minutes


Code P0156 Definition

Oxygen Sensor Circuit Malfunction (Bank 2, Sensor 2)

What Does P0156 Mean?

Your car has oxygen (O2) sensors that measure the amount of oxygen present in your exhaust. Based on the measurements taken, the O2 sensor will fluctuate between a high(rich) and low(lean) voltage reading. Your Engine Control Module (ECM) uses the voltage levels provided by your O2 sensors to regulate your engine’s fuel injector pulse. If you are seeing code P0156, it means that the O2 sensor behind your catalytic converter on bank 2 is malfunctioning.

What Are The Symptoms Of Code P0156?*

  • Check Engine Light
  • Decrease in MPG
  • Increased tailpipe emissions

*No noticeable adverse conditions in some cases

What Is The Cause Of Code P0156?

  • Faulty Bank 2 O2 sensor 2
  • Exhaust leak in front of sensor 2
  • Intake leak
  • Corrosion in connecter
  • Frayed or broken wiring

How Serious Is Code P0156? – Moderate


Driving with trouble code P0156 is acceptable but only for a short period of time. Driving with this code for an elongated period of time could result in greater engine or catalyst damage.

Code P0156 Common Diagnosis Mistakes

Replacing the O2 sensor without checking for any intake or exhaust leaks or loose connections.

Tools Needed to Diagnose:

How To Diagnose And Repair Code P0156?

Difficulty of Diagnosis and Repair – (2 out of 5)

  1. A sensor is needed for this next action, and the FIXD Sensor is perfect for it. Observe the live data from the O2 sensor and the fuel injector to see if they are both operating correctly.
  2. Note if the O2 sensor is rapidly or slowly switching from low to high voltage. This could indicate a faulty O2 sensor.
  3. Check for any broken or shorted wiring in relation to the O2 sensor. If there is any broken or shorted wiring, make sure to repair or replace it.
  4. Check for any vacuum leaks in the engine or any holes in the exhaust that could lead to air escaping from the engine. Repair any leaks or holes you find.
  5. At this point, if there are no intake or exhaust leaks, you should replace the bank 2 sensor 2 oxygen sensor.

Estimated Cost of Repair

For error code P0156, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

  • Oxygen sensor $200-$300
  • Exhaust repair $100-$200 (if welded to repair)
  • Vacuum leak $100-$200


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  1. P0156

  2. Neat little device

  3. If the issue is that either the O2 sensor or the fuel injector is faulty, your VEHICLE will need it to be replaced in order to run as efficiently as possible.


    Really, replace the vehicle due to a bad O2 sensor or fuel injector? Consider rewording this recommendation.

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