P0133 – Meaning, Causes, Symptoms, & Fixes

Code P0133 Definition

O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

What Does P0133 Mean?

The O2 sensor (Bank 1, Sensor 1) is meant to communicate with the Engine Control Module (ECM) about the air to fuel ratio of the engine, and adjust it accordingly. This is done in order to limit the amount of pollutants that your vehicle is emitting, and also control your car’s fuel consumption. Code P0133 is triggered when the voltage output that your O2 sensor is meant to send to your ECM does not change quickly enough in relation to the air to fuel ratio when you press on the gas pedal.

P0133 Symptoms *

  • Check Engine Light
  • Poor Fuel Economy
  • Excessive smoke from exhaust
  • Rough running engine
  • Poor idle
  • Possible Stalling

*No noticeable adverse conditions in some cases

P0133 Causes

  • Faulty O2 sensor
  • Faulty/Frayed wiring to the O2 sensor
  • Low Fuel Pressure
  • Possible Exhaust Leak
  • Possible Engine Vacuum Leak
  • Dirty Mass Air Flow sensor

Code P0133 Severity – Low 

This trouble code will most likely not prevent your vehicle from running, but it is still something that we recommend you get fixed as soon as possible. This code can cause harmful pollutants to be emitted from your vehicle into the air, which is extremely bad for the environment. You also will not be able to pass emissions tests with this code present.

 Code P0133 Common Diagnosis Mistakes

The most common diagnosis mistake is not doing a visual inspection of the O2 sensor or the Mass Air Flow sensor before replacing. Often times the O2 sensor’s wiring is frayed or the Mass Air Flow sensor is dirty, which can both trigger Code P0133 to occur. Exhaust and Engine Vacuum Leaks can also cause P0133 to be triggered.

 P0133 Diagnosis

  • Tools Needed to Diagnose:

 Difficulty of Diagnosis and Repair

  1. Check to see if there are any other codes along with P0133 and clear your Check Engine Light with FIXD.
  2. Check the freeze frame data in order to pinpoint the issue.
  3. Conduct a visual inspection of wiring around the O2 sensor for fraying or disconnection.
  4. Check the Mass Air Flow sensor to make sure that it is not dirty and possibly putting out false readings which affect the O2 sensor.
    1. If it is dirty , clean it, clear your codes using the FIXD device, and re-scan to see if the code is still triggered.
  5. Check for any leaks in the Exhaust or the Engine Vacuum.
    1. If there are, fix them, clear your codes using the FIXD device, and re-scan to see if the code is still triggered.
  6. If the problem persists, consider replacing the O2 sensor.
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Comments 6


October 23, 2018

where do I find my po133 sensor

FIXD Marketing

October 23, 2018

O2 sensor (bank 1, sensor 1) is located in front of the catalytic converter, towards the front of your engine.


Gary Ulibarri

November 11, 2018

Location of mass air flow sensor

Stan Henley

December 24, 2018

Mass airflow sensor will be in the air intake right after the air filter. Correct me if I’m wrong, FIXD.


January 4, 2019

I will replace the 02 sensors bank 1 and 2.


January 29, 2019

I have replaced the bank 1 and 2 02 sensors and also replaced the mass air flow sensor and the code and check engine light comes on now once the fuel gauge gets about a half a tank. I fill it up and it goes away until half a tank again.

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