Home TroubleshootingOBD Codes P0133: Meaning, Symptoms, Causes, And How To Fix

P0133: Meaning, Symptoms, Causes, And How To Fix

by Kelvin Yates

The error code P0133 indicates a problem with your vehicle’s oxygen sensors. The primary purpose of the oxygen sensor is to monitor the exhaust for gases for the oxygen content. The sensor communicates the data through a voltage reading with the powertrain control module (PCM). The computer system uses the transmitted data to regulate fuel injection in the engine.

When a vehicle ages, the exhaust pipe gets jammed with byproducts from the fuel burnings. When the oxygen sensor fails to detect the gases, the engine shows a steep decrease in fuel economy. The scanning process will display DTC P0133.

The oxygen sensor is a crucial part of a car’s engine system. Detecting the faulty oxygen sensor should lead to immediate action to repair it. If you want to know and understand P0133 deeply, you are at the right place.

P0133 Code

Code P0133 means a slow response is transmitted to the PCM from the oxygen sensor. The code deducts from ‘Oxygen Sensor Circuit Slow Response (Sensor 1)’. Typically the downstream oxygen sensor doesn’t respond in sync with the upstream oxygen sensor.


The slow response causes the PCM to detect errors and display symptoms like decreased fuel efficiency.

In this case, the laggy response of the oxygen sensor circuit transmits the voltage to the PCM. This inconsistent voltage response to the air and fuel ratio triggers symptoms. When PCM receives a delayed response, it emits excessive smoke from the exhaust. The vehicle also starts to respond negatively in terms of drivability.

P0133 Code Causes

You’ll need some diagnostics knowledge to evaluate oxygen sensor functions. If you’re not confident enough to do the troubleshooting, get help. Hire a professional technician for the task to avoid any unwanted problems.

Several causes might trigger the diagnostic trouble code P0133. It varies from one car to another. However, there are many common causes of the code. Sometimes the code could be caused by an inconsistent air-fuel ratio. Other times it could be caused by a faulty oxygen sensor in bank 1.

Here are a few causes to help start your diagnosis of the error code:

  • Exhaust system leak
  • Malfunctioning PCM
  • Faulty Oxygen Sensor
  • Damaged Wiring of the Oxygen Sensor
  • Dirty Mass Airflow (MAF) Sensor
  • Poor connection
  • PCM malfunction
  • Engine Vacuum leak

After scanning using an OBD II tool, if the code P0133 pops up, you’ll know where to start looking for faults. Although these are not the only causes of the error code yet, these are the most common ones.


P0133 Jeep

The most common causes of the error code in the Jeep Wrangler are wire harness issues and a bad O2 sensor. Sometimes the code might appear if the sensor is wrong for the system and the car starts displaying the code.

P0133 Ford

In Ford F-150, the code detection is usually caused by a bad sensor or a clogged-up exhaust manifold. The typical fix for the issue is sensor replacement.

P0133 Nissan

The symptoms of DTC P0133 in Nissan Pathfinder are that the exhaust starts to smell, and CEL is on. The engine might run rough and cause fuel by-product emissions. If you face these symptoms in your Pathfinder, it is an excellent time to get it checked.

P0133 Toyota

Toyota cars are famous for their durability and engine bulletproof-ness. If you see a P0133 code, then you should get it checked. Common code causes are similar to other vehicles discussed in this list.

P0133 Hyundai

When a Hyundai car reaches a certain age, the code may appear. The code is typically generated for several reasons, like a leaking exhaust manifold or a bad sensor. If you want to know the causes and fix for the P0133 Hyundai vehicles, click here.

P0133 Dodge

Dodge cars, just like any other vehicle, can run into the code P0133 on some occasions. The most common causes are lousy sensors, leaks in the exhaust manifold, and poor wiring.

How Do Oxygen Sensors Work?

An oxygen sensor inside a car is crucial for the engine system. It is responsible for monitoring the air and fuel mixture of the engine. The sensor is the primary source of information for oxygen exiting the exhaust system. It sends the data to the PCM to regulate the air and fuel mixture in the engine. This information is essential to the car as it helps the PCM run the vehicle smoothly.

The oxygen sensor interacts with the engine continuously. This communication assesses if the fuel is burning more oxygen than usual. Sometimes the engine burns way less oxygen than usual. The sensor starts to work at around 650 degrees Fahrenheit. Because of that, the sensor holds elements that can generate heat reasonably quickly.

For the rich air and fuel mixture, the sensor generates a small voltage, around 800-1000mv. If the air and fuel mixture is lean, it will produce about 100-200mv. The best part about the sensor is that it helps fuel efficiency and reduces harmful emissions.

Is The Code P0133 Serious?

Diagnostic Trouble Code P0133 is not as severe as other DTCs out there. The code is, in general, a mild one as it does not usually pose any immediate harm to the engine. It may produce drivability issues and pollutants during the malfunction. The code is responsible for monitoring the air and fuel ratio in the engine. During the code flashing, chances of decreased fuel efficiency are normal.

Although the P0133 code does not lead to any catastrophe, it may lead to a troubled driving experience. A secondary layer of a symptom, like an engine stalling, can appear. But, this is visible in rare cases. There is no clear answer to the seriousness of the code as the causes vary from car to car.

P0133 Code Common Symptoms

There are many indicators of the P0133 DTC. Some are more visible than others. If you witness the symptoms below, then it is likely that the O2 sensor is faulty.

1. Check Engine Light (CEL) Flashing

When the heated oxygen sensor bank 1 sensor 1 starts to respond slower, it will trigger the Check Engine Light. In this case, the PCM fails to maintain the engine’s required air and fuel mixture.

However, the check engine light is not triggered only for the code P0133. There might be loads of reasons why the light is flashing. The best way to understand the issue is through a thorough scan tool.


2. Low Fuel Efficiency

There might not be any CEL flashing for the code P0133. Instead, there might be a substantial amount of low fuel efficiency. The DTC P0133 O2 sensor circuit’s slow response (bank 1 sensor 1) causes the PCM to malfunction.

The PCM monitors the exiting oxygen through the exhaust using the oxygen sensor. When there is a lag in the system, the air and fuel mixture becomes inconsistent and burns more fuel than usual. Ultimately it causes low fuel efficiency.

3. Failure In Emission Test

If the PCM is not getting data, then the air-fuel mixture will not be in the optimum amount. Thus, the exhaust will eject the by-products of the fuel into the environment. If your car failed the emission test, then there is a good chance that the oxygen sensor has gone bad.

4. Engine Noise

When the downstream o2 sensor fails to provide the expected voltage to the PCM, it fails to operate correctly. The air-to-fuel mixture regulated by the PCM won’t be able to offer the optimum mixture for the engine. Thus, a lean mixture gets created, which causes a sound in the engine.

You can diagnose the system using OBD II if you face such symptoms. It helps to be sure about the noise’s origin.

5. Dark Exhaust Fumes

When a faulty oxygen sensor is present, the PCM can’t regulate the air to fuel mixture. The overall mix becomes inconsistent compared to a car with good O2 sensors. As a result, the car starts to produce dark exhaust fumes when it starts affecting the environment. The cause is generally insufficient combustion.

6. Overheating Engine

Although this is an uncommon symptom, the oxygen sensor is worn out excessively when it occurs. If this happens, you have overlooked the previous signs of a faulty oxygen sensor. This rare sign is a time bomb, which means the engine has started to get damaged. Be aware of the warning signs and take action immediately.

7. Bad Smell From The Tailpipe

A foul odor will be present if more fuel is in the engine than usual. The smell is similar to a musky rotten egg. This problem might be caused by either a faulty oxygen sensor or issues with fuel system parts. Due to the nature of the problem, it is best to scan the car properly before fixing it. It is recommended to address both the symptoms separately.

P0133 Diagnosis

DTC P0133 means “Oxygen Sensor Circuit Slow Response (Bank 1, Sensor 1)”. You are set if you have prior DIY experience and decent automotive knowledge. There are two ways to diagnose the code. One is automatic, and the other one is through visual inspection.

Automatic Diagnosis

Try scanning when you see that the Check Engine Light is on and other symptoms of a bad oxygen sensor. Several scanning tools can scan the car and easily display the diagnostic trouble codes. Use OBD II to scan the vehicle and look for codes popping up.

If you see P0133 in the display, then there is trouble with the oxygen sensor.

Visual Inspection

The faulty oxygen sensor is hardly the only reason for the code P0133 to pop up. There might be problems in the exhaust manifold, buildup on the O2 sensor, engine vacuum leak, or short wiring. A visual inspection is necessary to conclude a comprehensive diagnosis.

Even after identifying code P0133, it is not certain that the oxygen sensor is bad. However, it gives a streamline to follow and pinpoint the problem faster.

Certified mechanics can diagnose a problem more accurately than an average joe. We always suggest seeing a professional for diagnosis and fix in place of a DIY fix and diagnosis.

Is It Safe To Drive With Code P0133?

Code P0133 is a mild problem as it doesn’t affect the overall drivability. Any problem with the oxygen sensor is considered low in engine damage. However, if your check engine light is on and you found code P0133 flashing, you should check it.

It is not as harmful to the car as it is to the environment. The oxygen sensor is responsible for regulating the air and fuel mixture in the engine. Any irregularities with the sensor results in the emission of fuel by-products. It is harmful to the environment. Your car will likely fail the emission test with a faulty oxygen sensor.

How To Fix Code P0133?

DTC P0133 is caused by a low circuit input by the oxygen sensor to the PCM. There is no sure-shot way to fix this issue without properly diagnosing the problem.

1. Scanning The System

The first step to fixing the issue is to identify the problem. If you witness symptoms discussed in this article, it’s likely DTC P0133. Use a scan tool like OBD II to scan the system to identify the error codes. If there is more than one, the approach must be changed to address the issues separately.

2. Visual Inspection

After scanning the system and getting the DTC P0133, it is evident that you go through all the parts separately. This visual inspection eliminates the unnecessary need to change details prematurely.

Check the wiring, connectors, and oxygen sensor for defects. There might be a poor connection to the sensor, or it may come from the fuel injectors. Before stepping up to fix it, it is safe to be sure about the problem.

3. Exhaust Leak Check

Exhaust leakage can trigger the code P0133 in the scan tool. When a car reaches a certain age, the exhaust fills up with by-products from the fuel. It is especially true for vehicles that have periodic inspection and servicing.

Checking to see the leaks and clearing them may solve the slow response rate of the oxygen sensor.

4. Inspection Of MAF Sensor

Sometimes the engine’s mass airflow sensor can be damaged or require cleaning. It is also a reason why you can see the P0133 code. Make sure the sensor reading is good and has no carbon fouling. The code, in this case, can be cleared with just a cleaning of the system.

5. Sensor Replacement

You will need to change the sensor if every component is cleared and the code is still present. It is common to see a worn-out oxygen sensor in older cars. The main reason is that the driver failed to address all the symptoms for a long time. It causes significant damage to the sensor and the system.

Although P0133 is not a major issue, it can harm the environment. Changing the O2 sensor will lead to fuel efficiency and controlled emission.

How Much Will It Cost To Fix Code P0133?

DTC P0133 is relatively a cheap fix compared to the other DTCs. However, the cost relies on the code diagnosis and ease of access to the O2 sensor. Typically a diagnosis will cost $75 to $200 through a certified mechanic. If the diagnosis takes time, then the price will go up.

If the issue is not as severe as an engine failure, the cost is usually under $100. That includes the diagnosis, replacement parts, and labor. Make sure to go to a good technician for saving your time and effort. Cheap repair shops may cost you less, but it’ll cost you much more if they mess up anything.

The cost will vary depending on the issue. If the trouble is with the oxygen sensor, then it may cost $150 to $250. To repair exhaust issues, might cost you $80 to $150. If there are any vacuum leaks, you’re in for a repair worth $120 to $220.

Common Mistakes To Avoid While Fixing Code P0133

The most common mistake while fixing the code falls during the diagnosis of the problem. An average joe might dive into replacing the oxygen sensor after the diagnosis. But, it opposes a bigger problem. Code P0133 pops up for several reasons. There might be an exhaust system leak, PCM malfunctioning, or even damaged wiring of the oxygen sensor.

It’s the number one reason oxygen sensor codes keep coming back. Sometimes heated oxygen sensor bank 1 sensor 1 can cause irregular behavior. Therefore, to ensure the O2 sensor slow response fix, inspect all the components manually to pinpoint the solution.

P0133 Trouble Code and Oxygen Sensor Circuit Issues – Need-to-Know Facts

  1. The P0133 trouble code indicates that the vehicle’s oxygen sensor is having a problem and not transmitting signals quickly enough to the car’s computer.
  2. The oxygen sensor measures the amount of oxygen coming out of the engine and helps calibrate the amount of fuel going into the engine to maintain the optimal ratio between air and fuel, minimizing fuel consumption and pollutant emission.
  3. Symptoms of oxygen sensor circuit issues include decreased gas mileage, misfiring or stalling engine, and worsening engine performance.
  4. Other issues that could cause slowness in transmitting voltage reading from the sensor include soot or oil buildup on the oxygen sensor, faulty wiring, leaking vacuum or intake manifold line, incorrect fuel pressure, and dirty or malfunctioning mass air flow sensor.
  5. Cleaning away any buildup on the oxygen sensor, fixing faulty wiring, and replacing or fixing leaking lines can resolve P0133 issues.
  6. Incorrect fuel pressure can cause erratic oxygen sensor readings and should be addressed promptly.
  7. A malfunctioning oxygen sensor can be replaced to resolve P0133 issues.
  8. P0451 and P0141 diagnostic codes also relate to oxygen sensor circuit issues and can be resolved by fixing the root cause.
  9. Failing an emissions test can result from issues with the oxygen sensor, indicating the importance of resolving oxygen sensor circuit issues promptly.
  10. OBD-II scanners can help diagnose trouble codes related to oxygen sensor circuit issues, and products like OBD readers and scan tools are available to help with diagnosis and resolution.


P0133 is not as severe as some other diagnostic trouble codes. In most cases, the code is minor and does not impact the engine. During the malfunction, it may cause drivability problems and pollution.

Although the P0133 code has yet to cause a disaster, it may cause you to have difficulty driving. A secondary layer of a symptom can arise, similar to an engine stalling. However, this only appears in a few instances.

If you see the symptoms of DTC P0133, then you should get it checked as soon as possible. Early fixing will lead to a smooth driving experience and free from trouble.


Here are some popular FAQs:

How To Fix The P0133 Code

The first step in resolving a problem is to recognize it. If you’re experiencing any of the symptoms listed in this post, you’re likely dealing with DTC P0133. Hence, to determine the fault codes, scan the system with a scan tool such as OBD II. After scanning the system and receiving the DTC P0133, we recommend you go through all the parts individually. This visual check reduces the need for premature part replacement. The code P0133 in the scan tool can be caused by exhaust leakage. The delayed response rate of the oxygen sensor could be solved by looking for leaks and cleaning them. After clearing all components, you will need to change the sensor if the code persists.

What Does Code P0133 Mean

P0133 means the oxygen sensor sends a slower response than usual to the PCM. Oxygen Sensor Circuit Slow response in bank 1 sensor 1 is deducted from the code P0133. The downstream oxygen sensor usually does not react the same way as the upstream oxygen sensor. So, the PCM detects the problem and displays symptoms such as decreased fuel efficiency. It comes as a result of the slow response. The slow voltage in this scenario is transmitted to the PCM due to the oxygen sensor circuit’s slow reaction. Symptoms trigger due to the inconsistency of the voltage response to the air/fuel ratio. When PCM receives a delayed answer, it emits excessive smoke from the exhaust system. In addition, the vehicle’s drivability begins to suffer.

What Can Cause A P0133 Code

Several things can cause the diagnostic issue code P0133. It differs from one vehicle to the next. There are, however, several common causes of the error code. An uneven air-fuel ratio sensor can sometimes produce an error. It could also be due to a malfunctioning oxygen sensor in Bank 1. Here are a few possible factors to assist you in diagnosing the problem code… A leak in the exhaust system, or a faulty PCM sensor. Or, it could be a damaged oxygen sensor wiring or a dirty mass airflow (MAF) sensor with a bad connection. If the code P0133 appears after scanning with OBD II, you’ll know where to hunt for defects. Although they are not the sole cause of the error code, they are the most common. So, be sure to have a lookout for them!

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