Skip to Content

P0133 Fault Code – What It Means and How to Fix It

Never a good time for a check engine light; not to worry, I’m John Cunningham, a qualified mechanic, and very shortly, you’ll have a good idea of what’s causing your MIL and how to fix it; let’s get stuck in.

On this page, we’ll cover the following:

What is the P0133 code?

The P0133 code is a diagnostic trouble code (DTC) that refers to an issue with the oxygen sensor’s response time.

oxygen sensor

Specifically, it indicates that the oxygen sensor located in the exhaust system’s upstream (closest to the engine) side of bank one is not responding as quickly as it should be.

What does the oxygen sensor do?

The oxygen sensor plays a vital role in your car’s fuel system. It measures the amount of oxygen in the exhaust gases and sends a signal to the engine control module (ECM) to adjust the air-to-fuel ratio. This ensures that the engine is running efficiently, reduces emissions, and helps to prolong the life of your vehicle.

P0133 Symptoms

Here are the top 7 symptoms associated with this fault code:

  1. Check engine light is on: The most common symptom of the P0133 fault code is that the check engine light will illuminate on your dashboard.
  2. Decreased fuel efficiency: When the oxygen sensor is not functioning properly, it can cause your engine to burn more fuel than necessary, resulting in decreased fuel efficiency.
  3. Poor engine performance: A faulty oxygen sensor can also cause your engine to run poorly, reducing acceleration, hesitation, or rough idling.
  4. Bad smell from exhaust: If the oxygen sensor is malfunctioning, it can cause an excess of fuel to be burned in the engine, resulting in a strong smell of gasoline coming from your exhaust.
  5. Failed emissions test: The P0133 code can cause your vehicle to fail emissions tests, as it indicates that your engine is not burning fuel efficiently, leading to increased emissions.
  6. Engine misfires: In severe cases, the P0133 fault code can cause engine misfires or stalling, which could be a serious safety concern.
  7. Other fault codes: If the oxygen sensor is not functioning properly, it can cause other fault codes to appear, including P0140, P0130, and P0150, which all relate to the oxygen sensor.

What causes the P0133 code?

Several factors can cause the P0133 code to appear, including:

  • A faulty oxygen sensor
  • Wiring issues (e.g., damaged wires or poor connections)
  • A clogged or dirty air filter
  • A vacuum leak in the intake manifold or air intake system
  • An exhaust leak or damaged exhaust system components
  • A malfunctioning ECM or other control module

How do you diagnose the P0133 code?

To diagnose the P0133 code, you’ll need an OBD-II scanner or code reader to retrieve the code from the ECM. Once you have the code, you can inspect the oxygen sensor, wiring, air filter, and intake and exhaust systems for any issues.

o2 sensor

You can also use a multimeter to test the sensor’s resistance and voltage output to determine if it’s functioning correctly.

How do you fix the P0133 code?

Fixing the P0133 code will depend on the underlying cause. Here are some potential solutions:

  • Replace the oxygen sensor if it’s faulty or damaged
  • Repair or replace any damaged or corroded wiring or connections
  • Clean or replace the air filter if it’s clogged or dirty
  • Check for and repair any vacuum leaks in the intake system
  • Repair any exhaust leaks or damaged exhaust components
  • Reset the ECM and monitor the system for any further issues

Sum Up

The P0133 code can be tricky to diagnose and repair. Still, addressing it as soon as possible is essential to prevent further damage to your vehicle’s engine and emissions system.

About the Author

This article was created with the assistance of AI technology to aid the author, John Cunningham, who is a seasoned Red Seal-certified auto technician with more than 25 years of experience in vehicle repairs. However, please note that John Cunningham has edited the content to ensure accuracy and quality.

You may find the following links helpful: