Air & Fuel Mixture ControlOBD2 Codes

P0133 – Meaning, Causes, Symptoms, & Fixes

Reading Time: 2 minutes


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 number 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 quick enough in relation to the air to fuel ratio when you press on the gas pedal.

What Are The Symptoms Of Code P0133?

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

*No noticeable adverse conditions in some cases

What Is The Cause Of Code P0133?

  • Faulty O2 sensor (most common)
  • Faulty/Frayed wiring to the O2 sensor
  • Exhaust Leak
  • Engine Vacuum Leak
  • Dirty Mass Air Flow sensor

How Serious Is Code P0133? – 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 it. 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.

Tools Needed to Diagnose:

How To Diagnose And Repair Code P0133?

Difficulty of Diagnosis and Repair (1 out of 5)

  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 and connector at 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. 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 exhaust or vacuum leaks. If there are any, 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 bank 1 pre-catalytic converter O2 sensor.

Estimated Cost of Repair

For error code P0133, 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. where do I find my po133 sensor

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

      FIXD Team

      1. Hello i have a quesrion i have a crown Victoria ex police and,i have the code p0133 so i pit a new o2 sensor and,i delet the,code,but is still show me,the,code and,the,car feel run roughly and,i hear by the gas thank a whistle so i think is a vaccum there. So can u help me,please thank you

      2. I clean the mass air flow sensor too and,is the same code on i installed a new fuel pressure too

  2. Location of mass air flow sensor

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

  3. I will replace the 02 sensors bank 1 and 2.

  4. 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.

    1. Mine does the same thing. It appears like there is a vacuum leak in the line from the fuel tank to the charcoal canister, or vacuum source to the fuel tank. I am told a smoke test at a repair shop is required to find the leak.

      1. I have exactly the same problem as Art has. Plus, I get kinda “drum” noise from the fuel tank as if something is blowing air on a closed circuit piece of cardboard. I figured when I open the gas tank lid, soda can effect pops up as if there was some pressure that was released and then noise goes away.

        I have replaced O2 sensor, and now converter as well.

        Don is right. There is most likely a vacuum link. My fuel consumption is exorbitant, hardly 18-19 mpg combined when it is supposed to be 22/37 mpg for my fusion.

        How did you perform the smoke test, and what was the remedy? Any help would be appreciated

      2. I have a 2004 Hyundai Sonata code p0133 where is the O2 sensor location bank 1 sensor 1 on my vehicle

  5. How much do I charge to replace the sensors

  6. Does FIXD work on different vehicles

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