How to Fix P0139 Code: A Comprehensive Guide

A p0139 code is a trouble code that is triggered when there is a malfunction in the downstream oxygen sensor circuit. This sensor is located after the catalytic converter and monitors the level of oxygen in the exhaust gases to ensure that the catalytic converter is working correctly to reduce emissions. When this code is displayed, it means that there is a defect in the oxygen sensor circuit which can cause various issues like poor vehicle performance, reduced fuel economy, and increased emissions. In this article, we will discuss how to fix p0139 code and get your car back on the road.

How to Fix P0139 Code: A Comprehensive Guide


What Is A P0139 Code?

P0139 is a diagnostic trouble code that appears when the oxygen sensor downstream of catalytic convertor fails to provide enough data to your vehicle’s computer, resulting in an inconsistent reading. The oxygen sensor is responsible for transmitting data on the exhaust’s oxygen levels to the engine control module (ecm).

When this sensor fails, it can cause a host of problems that may impair your vehicle’s drivability and overall operation.

Common Causes Of The P0139 Code

A p0139 code can be caused by a variety of factors, ranging from a faulty oxygen sensor to a blown fuse.

  • A malfunctioning oxygen sensor
  • An oxygen sensor wiring issue
  • A blown oxygen sensor fuse
  • Fuel and air mixture imbalances
  • Engine problems

Symptoms Of P0139 Code

A p0139 code can produce a range of symptoms that may impact your vehicle’s drivability.

  • Decreased fuel efficiency
  • Engine stalling
  • Rough engine performance
  • Increased exhaust emissions
  • Check engine light

Importance Of Fixing P0139 Code

If your check engine light is on and you have received a p0139 code, you should take it seriously and have it diagnosed and repaired. Failure to fix this code can result in severe engine or transmission problems, leading to costly repairs down the line.

Additionally, a malfunctioning oxygen sensor can result in decreased fuel mileage and increased emissions, potentially affecting your vehicle’s environmental impact.

How To Check For P0139 Code In Your Vehicle

It’s simple to diagnose a p0139 code with a scan tool.

  • Connect the scan tool to the diagnostic port of your vehicle.
  • Turn on the engine.
  • Scan the vehicle’s computer system to detect any stored codes.
  • Check for the p0139 code and take note of any other related codes.
  • Once you have identified the issue, have it repaired by a professional.

A p0139 code is a serious trouble code that requires immediate attention. Fortunately, diagnosing and repairing it is simple, so make sure you take your vehicle to an auto repair specialist as soon as you see the check engine light turn on.

Step-By-Step Guide To Fixing The P0139 Code

If you own a car, you’re most likely familiar with the agony of seeing the p0139 code appear on your dashboard. This code, also known as the oxygen sensor circuit slow response (bank 1, sensor 2), indicates that your car’s oxygen sensor is not working as it should.

  • Locate the bank 1 sensor 2 oxygen sensor: the bank 1 sensor 2 is located behind the catalytic converter in most vehicles.
  • Disconnect the wiring harness: disconnect the wiring harness from the oxygen sensor by pressing the tab and pulling it out gently.
  • Remove the sensor: using an oxygen sensor wrench, remove the sensor from the exhaust pipe.
  • Install a new oxygen sensor: insert a new oxygen sensor into the exhaust pipe and tighten it with the wrench.
  • Reconnect the wiring harness: connect the wiring harness back to the new oxygen sensor.
  • Clear the code: use an obd-ii scanner to clear the p0139 code. If you don’t have a scanner, you can remove the negative terminal of your car’s battery for a few minutes to reset the code.

Diy Vs Professional Fix: Pros And Cons

While fixing the p0139 code yourself can be cost-effective, it may not always be the best option.

Diy pros:

  • Save money on labor costs
  • Learn about your car
  • Control over the repair process

Diy cons:

  • Risk of causing more damage
  • Limited knowledge and tools
  • Time-consuming process

Professional pros:

  • Expertise and experience
  • Warranty on the repair work
  • Access to specialized tools and equipment

Professional cons:

  • Higher labor costs
  • Limited control over the repair process
  • Possible delays due to scheduling conflicts

Tools Needed To Fix P0139 Code

Before you start fixing the p0139 code, you should have the following tools:

  • Oxygen sensor wrench
  • Obd-ii scanner
  • Safety glasses
  • Gloves

Cost Of Fixing P0139 Code

The cost of fixing the p0139 code varies depending on whether you choose a diy or professional fix. If you choose to fix it yourself, the cost will be for a new oxygen sensor and potentially an oxygen sensor wrench if you don’t already have one.

If you opt for a professional fix, the cost will include labor fees and the price of the oxygen sensor.

A diy fix will likely cost between $20-$100, while a professional fix can cost between $150-$500. It’s worth keeping in mind that prices can vary depending on the make and model of your vehicle as well as the location of the repair service.

How to Fix P0139 Engine Code in 3 Minutes [2 DIY Methods / Only $8.24]

Fixing Specific Causes Of P0139 Code

If you’ve got a p0139 code, it’s more than likely due to a faulty o2 sensor or catalytic converter, or exhaust system leaks. Other causes may be an engine vacuum leak, issues with the powertrain control module (pcm) or engine control module (ecm).

Let’s have a look at how to fix these issues.

Fixing Faulty O2 Sensor

The o2 sensor works by monitoring the oxygen levels in the exhaust and sending this data to the pcm/ecm. If the o2 sensor isn’t functioning well, your car’s fuel system won’t work properly, leading to poor fuel economy.

Here are a few common fixes for a faulty o2 sensor:

-replace the sensor if it’s completely dead or malfunctioning

-check for issues with the wiring or connectors around the sensor

-clean the o2 sensor, it may just need a good cleaning

Repairing Or Replacing Catalytic Converter

The catalytic converter, which is usually located between the muffler and the exhaust manifold, turns harmful gases into less harmful ones, like carbon dioxide. It’s not unusual for these to wear out eventually, which could lead to a p0139 code.

Here are ways to address faulty catalytic converters:

-replace or repair the catalytic converter if it’s damaged

-check for clogging – this may be causing the issue, and it’s a lot cheaper to address

-professional cleaning, it’s the easiest fix if there’s no significant damage

Correcting Exhaust System Leaks

Leaks in the exhaust system can lead to a p0139 code, and this could mean troubles for your car. Generally, exhaust system leaks occur at one or several points, like loose or broken bolts or a hole in the muffler.

Here’s what to do if you have an exhaust system leak:

-find the leak – this is essential before you can fix it

-replace the damaged part – this depends on where the leak is located

-check your bolts – always make sure they’re tight and free of rust

Fixing Engine Vacuum Leaks

Vacuum leaks can hinder engine performance, leading to a p0139 code. This usually happens when air gets into the engine via car body fittings or hoses.

Here are simple solutions to vacuum leaks:

-check the engine for vacuum leaks – unplug one by one the vacuum hoses and check for hose integrity by spraying carburetor cleaner.

-replace or repair the damaged part quickly

– don’t let vacuum leaks go unchecked, it will cause other issues

Replacing Pcm Or Ecm

If the above solutions don’t work for you and the issue persists, it’s likely that there’s a problem with the pcm or ecm. It’s advisable to consult a professional mechanic before trying anything yourself. They will diagnose your car and provide the recommended course of action.

Fixing a p0139 code may range from simple tasks like cleaning to substantial repairs like replacing the pcm or ecm. In any case, it is important to act right away before the issue escalates. By taking a little bit of effort and utilizing some basic knowledge and skills, you should be able to address a p0139 code without spending excessively.

Maintenance Tips For Avoiding P0139 Code

Are you tired of constantly getting the p0139 code and not knowing how to fix it? Don’t worry, you’re not alone! The p0139 code is one of the most common codes that vehicle owners encounter. It relates to an issue in the oxygen sensor circuit, which can cause trouble to your vehicle’s engine performance.

In this blog post, we will be discussing the maintenance tips that can help you avoid the p0139 code in the future. So, let’s get started!

Importance Of Regular Vehicle Maintenance

Regular maintenance of your vehicle can help prevent a lot of problems, including the p0139 code.

  • saves money: regular maintenance can help prevent major repairs, which can end up costing you a lot in the long run. Fixing a minor issue is always less expensive than a major one, so it’s better to be proactive than wait for a big problem to occur.
  • increases safety: regular maintenance ensures that all the parts of your vehicle are working correctly, which makes it safer to drive. For example, a faulty oxygen sensor can result in poor fuel efficiency, which can lead to an unexpected breakdown.
  • increases vehicle lifespan: regular maintenance can help your vehicle last longer. When you take care of your vehicle, it takes care of you. This can help you in the long run as you won’t have to invest your money, time, and energy into buying a new vehicle.

How To Prevent Future P0139 Code Occurrences

Preventing the p0139 code from occurring again can be done in several ways.

  • regular inspection of oxygen sensor: your vehicle’s oxygen sensor needs to be inspected and replaced regularly, ideally every 60,000 to 90,000 miles. This can help avoid any additional problems that result from the faulty oxygen sensor.
  • proper fuel: make sure you use the right fuel for your vehicle, as the wrong type of fuel can damage the oxygen sensor or cause an incorrect reading.
  • avoid short trips: short trips can damage the oxygen sensor, as the sensor takes some time to heat up and get a correct reading. It is always better to take a longer trip if possible or combine multiple short trips into one long trip.
  • avoid overloading: overloading your vehicle can put extra strain on the engine, including the oxygen sensor. Make sure you don’t exceed the recommended weight limit for your vehicle.

Recommended Maintenance Schedule For Your Vehicle

Every vehicle is different, but here is a general maintenance schedule that is recommended:

  • oil change: every 5,000-7,500 miles or every six months.
  • tire rotation: every 5,000-7,500 miles.
  • brake inspection: every 10,000 miles or annually.
  • air filter replacement: every 15,000-30,000 miles.
  • spark plug replacement: every 30,000 miles.
  • o2 sensor inspection and maintenance: every 60,000-90,000 miles.
  • timing belt replacement: every 60,000-100,000 miles.

Regular vehicle maintenance is essential in avoiding the p0139 code in the future. By following the maintenance tips discussed in this article, you can save yourself time, money and avoid the stress of dealing with unexpected vehicle breakages. Remember to check your vehicle’s owner’s manual or consult with a professional mechanic for any other recommended maintenance steps specific to your vehicle.

Frequently Asked Questions (Faqs) About P0139 Code

What Happens If I Leave The P0139 Code Unfixed?

Ignoring the p0139 code means you are potentially jeopardizing your vehicle’s safety and performance. The oxygen sensor is responsible for detecting the fuel and air mixture in the engine and sending it to the vehicle’s computer.

  • Decreased fuel efficiency.
  • Engine misfires and stalling.
  • Catalytic converter damage.
  • Increased emissions.
  • Damage to spark plugs, oxygen sensors or other engine components.

How Long Can I Drive With The P0139 Code Before Fixing It?

It is recommended to fix p0139 code as soon as possible, to avoid further damage to your vehicle. The longer you drive with a defective oxygen sensor, the more harm it may cause your engine, which can lead to long term and more costly repairs.

Can I Still Pass An Emissions Test With A P0139 Code?

No, your car cannot pass an emissions test if there is a p0139 code present. The p0139 code means that there is an issue within the oxygen sensor circuit, which affects the vehicle’s fuel and air mixture. Your vehicle needs to pass its emissions test to be legally allowed on the road.

Failure to pass the test due to a p0139 code will require you to repair the issue first.

What Other Codes Are Related To The P0139 Code?

Most engine codes that start with a “p” refer to the powertrain, such as the transmission or engine.

  • P0130: oxygen sensor circuit malfunction (bank 1, sensor 1).
  • P0131: o2 sensor circuit low voltage (bank 1 sensor 1).
  • P0133: o2 sensor circuit slow response (bank 1 sensor 1).
  • P0134: o2 sensor circuit no activity detected (bank 1 sensor 1).

How Do I Troubleshoot And Fix Other Obd-Ii Codes?

If your vehicle has any other obd-ii codes, refer to your vehicle owner’s manual. It will provide you with the necessary steps needed to troubleshoot and fix the particular code.

  • Clearing the code, and driving the car to see if the code comes back on.
  • Checking the voltage and resistance of the sensor and replacing if necessary.
  • Checking the wiring and connections to the sensor and repairing if needed.

It is always recommended to seek professional help from a qualified mechanic to fix the obd-ii code of your vehicle. By following these steps, you can solve the p0139 code and other obd-ii codes, ensuring your vehicle continues to perform safely and efficiently on the road.


Based on the information provided, it’s clear that the p0139 code can be a frustrating issue for any vehicle owner. However, by following the steps outlined in this blog post, fixing this code is certainly achievable. By first determining the root cause of the issue with the oxygen sensor, checking the wiring and connections, and potentially replacing the sensor altogether, it’s possible to get your vehicle running smoothly once again.

Taking the time to address any underlying issues with the vehicle’s exhaust system can also prevent the p0139 code from reoccurring in the future. While the process may seem daunting at first, by utilizing the resources available and thoroughly troubleshooting the issue, drivers can save both time and money in the long run.