OBD Code P0131 – What Does This Mean? How Can It Be Fixed?

OBD code P0131 is a generic trouble code that means there is an issue with your car’s oxygen sensor.

The oxygen sensor measures the amount of unburned oxygen in the exhaust, which helps determine how much fuel should be added to the engine.

P0131 comes up when there is either not enough voltage or no voltage at all going to the oxygen sensor circuit.

It is triggered when the ECM (or PCM) detects an unusually low voltage reading from one of the oxygen sensors.

When this happens, it means that either the O2 sensor itself isn’t working properly and can’t send a signal to tell the ECM that its job is done or, the ECM isn’t sending the right amount of voltage to power the O2 sensor or ground it properly so that it can send its signal back up to the PCM.

The P0131 code doesn’t tell you which is causing your engine light to come on. You need additional diagnostics tests to find out if there’s something wrong with your O2 sensor or if something else needs repair.

Symptoms of OBD Code P0131

1. Check Engine Light Stays On

If you’re seeing the Check Engine light come on, then you might be experiencing a P0131 code.

The check engine light should illuminate when there is an issue with your vehicle and it will turn off once the problem has been fixed.

If your check engine light stays on for more than three days, it could mean that there is a serious malfunction in your vehicle that needs to be addressed by a professional mechanic immediately.

To diagnose this error code and fix it before it causes any other problems with your vehicle, pay attention to what else is going wrong when this happens (in addition to seeing this specific code).

For example: Is there a noticeable lack of power? Do all functions seem normal except for acceleration? Are there any noises coming from under the hood or from inside the cabin?

2. Lack of Power

A lack of power can be caused by many things, including a bad O2 sensor, a bad ECM (engine control module), or even a faulty exhaust manifold gasket.

If there’s too much or too little oxygen in your engine’s exhaust stream, your O2 sensor will detect it and adjust accordingly to make sure it gets as close as possible to ideal conditions.

The ECM then uses this information to determine whether fuel injection needs adjusting based on how your car reacts when you are driving. This information helps you to diagnose the problem early.

3. Exhaust Odor

If you smell something burning when you’re driving, the most likely cause is a leak in your exhaust system.

When an exhaust system leaks, the escaping fuel will burn and produce smoke or fumes that can be smelled and seen by others.

Exhaust leaks can also cause poor fuel economy and poor performance due to unmetered air entering the combustion chamber of your engine.

Exhaust odor is usually caused by cracked exhaust manifolds or cracked exhaust pipes.

A leaky manifold gasket is less likely because it won’t allow enough air into the engine to produce a noticeable odor, but it can happen nevertheless.

4. Engine Runs Roughly

If you have a rough idle, it could be caused by any number of problems in your engine.

You may have a vacuum leak that’s causing the idle to fluctuate or a dirty mass airflow sensor.

It’s also possible that your spark plugs aren’t firing properly or there are issues with one of your coils.

Most modern cars run on an electronic fuel injection system that uses sensors throughout the engine to determine how much fuel needs to be added at any given moment.

If these sensors fail for any reason, it can cause the car to run roughly and other engine issues may arise as well.

A code scanner will let you know what components were responsible for triggering this OBD2 trouble code so you know where to start looking for problems in your vehicle’s diagnostic system.

5. Possible Exhaust Leaks

The first thing you should do is check for exhaust leaks. An exhaust leak can be as small as a loose connection or a hole in the manifold gasket, or it can be as large as a hole in your muffler or catalytic converter.

This may not always cause an OBD code P0131, but it’s still something to look out for and address if you find one.

There could also be some clog in the muffler. You can check out this post on how to clean a clogged muffler.

If you don’t find any exhaust leaks when you check your vehicle, then the next step is to get a professional diagnosis of why this code has been triggered.

This could involve a deeper inspection of your car’s computer system. The technician will run tests on each sensor individually and compare readings with known data from working sensors so they can determine whether something is faulty or not.

Read: OBD Code P2196

Causes of OBD Code P0131

1. Bad O2 Sensor

The most common cause of this issue is a bad O2 sensor. To figure out if your sensor is causing the problem, you’ll first need to remove it from the vehicle and test it.

If there are any signs of damage, corrosion, or cracks in the sensor, then you should replace it.

O2 sensors can fail for one of two reasons: either they become clogged or they short out against their wiring harness.

In either case, you may need to replace your O2 sensor if it’s causing your check engine light to come on.

If you do not replace it, your car will continue consuming too much gas and potentially damaging itself.

If you don’t find any obvious problems with your oxygen sensor when testing it, then I recommend that you continue to check other components to isolate where exactly this problem originates. It could be something else entirely.

2. Faulty ECM

Check the ECM. You can check the ECM by using a voltmeter to test for power at the ECM connector.

If you see 12 volts, then it’s likely that there’s an electrical problem somewhere else in your system.

If you don’t see any voltage at all, then your problem may be with the ECM itself and not with its wiring harness or O2 sensor.

Check for poor connections to other parts of your engine control system (ECS). If there are any loose or damaged wires at this point, it can cause P0131 to appear on your dash.

It’s also worth checking if any connectors need cleaning or replacement before continuing with tests on other components in this system.

3. Leaking Exhaust Manifold Gasket

A leaking exhaust manifold gasket is a common cause of this code, and you can easily check for leaks by spraying soapy water on the exhaust manifold.

If bubbles form around any fasteners or unions, your gasket is likely to be leaking.

If you see any cracks or holes, you will need to replace the manifold. You can also check for leaks by removing the exhaust manifold.

While it’s off, you should inspect the inside of it with a light source shining into it from behind to look for fluid stains and discoloration that may indicate a leaky gasket.

4. Exhaust Leaks

Exhaust leaks are another common cause of this code. When there is an exhaust leak, the OBD system will detect the higher-than-normal pressure in the exhaust system and set a P0131 code.

Exhaust leaks can occur anywhere along the exhaust system from the catalytic converter to any hanger brackets or gaskets.

If you have determined that it is indeed an exhaust leak, you should repair any holes or cracks in your vehicle’s exhaust system as soon as possible to prevent further damage to other parts of your vehicle.

If you have a large enough hole in your catalytic converter or muffler section, it may require a new catalytic converter or muffler assembly altogether.

5. Low Fuel Pressure

If your fuel pressure is low, it can cause a P0131. To check the fuel pressure you will need to use a fuel pressure gauge.

A good rule of thumb is that the ideal fuel pressure should be between 40 and 60 psi (pounds per square inch).

If your vehicle’s engine uses an electric fuel pump, you may want to look up how to replace the electric pump or just give it to a professional.

How to Fix OBD Code P0131

1. Check For Faulty Oxygen Sensors

If you’re getting an OBD P0131 code, the first thing to do is check the sensor(s). The O2 sensors are built into your vehicle and they measure whether or not there is sufficient oxygen in your exhaust system.

Replace the O2 sensor with a new one. If you have an older car, it may be time to replace your O2 sensor(s).

This will often fix this type of problem as well as other issues like rough idling, poor gas mileage, and others.

2. Replace Exhaust Manifold Gasket

a. Remove the exhaust manifold

You can find the exhaust manifold at the front of your engine. It’s held on by a few bolts and needs to be removed.

b. Install a new gasket

Once you’ve removed the old gasket, you’ll need to install a new one. The best way to do this is by tapping it into place with a rubber mallet or something similar.

c. Reinstall your exhaust manifold

With your new gasket in place, reattach your exhaust manifold by tightening down each bolt first before proceeding to the next one.

Keep track of which bolts go where so that everything goes back together correctly.

3. Get The Car Diagnosed And Fixed By A Professional

Get your car diagnosed by a professional mechanic. You can find one at a local repair shop.

Once they diagnose the problem, they should be able to give you an estimate on how much it will cost to fix and how long it will take them.

If this sounds like something that might work for you, then go ahead and book an appointment as soon as possible.

If replacing the part sounds too expensive or time-consuming for now, then consider buying some aftermarket parts online from sites like Amazon or eBay.


Engine codes are used to diagnose engine problems in your vehicle. These codes indicate a problem with a certain component in your car and if not fixed immediately, can result in more serious problems later on down the road.

The most common causes of the OBD code P0131 include exhaust leaks, leaking exhaust manifold gasket, faulty 02 sensors, faulty ECM, or low fuel pressure.

If you keep seeing the P0131 code, it’s important to have it diagnosed at once by a professional mechanic who has experience dealing with these issues so that they won’t become major issues along the way.