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How to Fix P0171 Code: “System Too Lean (Bank 1)”

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If you're searching for how to fix the P0171 code, confirm that the error code exists using an OBDII scanner. Then, try one of two common DIYs to fix the P0171 code: cleaning the MAF sensor or replacing the oxygen sensor. If none of the methods work for you, you need to take your vehicle to a repair shop and have them perform manufacturer tests to resolve the issue. 

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Check engine light is one of the most important elements that any driver must keep an eye on. The check engine light may be linked to simple issues like a loose fuel cap and indicate a significant problem related to complete engine failure.

To stay on the safe side, whenever you see a check engine light, it is important to take the problem seriously and resolve it as soon as possible to prevent major complications down the road.

P0171 code is a very common error that you might notice in any vehicle, which is most likely related to a problem with the air-fuel mixture ratio. There are basically indicates that there is more air than fuel in this mixture, which is not good, and we usually refer to it as the system running lean.

This article provides you with all in just a note to understand the P0171 code. We highlight its definition, explanation, causes, symptoms, repair options, and expected repair costs. 

What is the P0171 code definition?

The P0171 error code's main definition is “System Too Lean (Bank 1).” To better understand this definition, it is crucial for you to go through the basics that involve when your fuel is lean versus when it's too rich. We will cover this basic in the following section to help you determine whether the P0171 error code is serious or not. 

What does the P0171 code mean? 

Any vehicle running on a combustion system should have a certain level of air to fuel mixture. If this mixture did not have the right air to fuel ratio, your vehicle would not run properly, and you will see some issues in the overall performance.

For instance, having too much fuel is not a good thing, and your vehicle will throw an error displayed in the form of a check engine light illuminating. In the same manner, when there is too much oil or in other words, when there is not enough fuel, your vehicle will be running lean, which usually is displayed with a check engine light illuminating and associated with a P0171 code if the issue is on the Bank 1 and another code if the issue is affecting Bank 2 of your engine.

What are the primary causes for the P0171 code?

As we indicated before, when your vehicle has a P0171 code, the problem could be related to very few fuel supplies or too much air supply.

Depending on what's the real culprit of this error, the causes can be a little different.

Let's take a closer look below:

  • When the P0171 code is triggered due to too much airflow 

The problem is most likely related to mass air flow sensors, faulty vacuum leaks, or bad oxygen sensors.

  • When the P0171 code is triggered due to too little fuel supply

If that's the case, the problem is most likely due to a bad Fuel filter, faulty fuel injector, or malfunctioning fuel pump. 

Keep in mind that they mentioned causes are the very common primary reasons for a P0171 code. However, there might be additional car parts associated with certain model years of certain brands. Therefore, you need to consider reviewing other items if none of the common DIYs help you fix the P0171 code. That's where the mechanic repair shop can come in handy. 

How do I know if it’s the P0171 code? Symptoms of the P0171 code

It's very important to detect the P0171 code immediately after it occurs to prevent major complications to your vehicle. That's why we recommend you as a driver to familiarize yourself with the common symptoms of the P017 code. These symptoms usually include:

  • Check engine light illuminating
  • Engine misfiring
  • Engine running rough when idling
  • Engine coughing
  • Reduction in the engine's power

Keep in mind that all these symptoms can be linked to various other options, and it's hard to tell whether it's a P017 code unless you use an OBDII scanner and check the error code on the screen. 

P0171 code diagnostics: How do I fix the P0171 code?

When dealing with a P0171 code, some suggested DIY's by professional mechanics and automotive experts to help you resolve the problem from home without needing a professional mechanic. The good news here is that these DIYs should work most of the time, which means that you don't have to worry about labor costs.

Let's take a closer look at some of the recommendations on how to fix the P0171 code at home

  • Can you confirm the error? 

Before we list the different DIYs to help you fix the P0171 code, it is important first to take a step back and confirm that your vehicle has this error.

To do so, you can use a simple OBDII scanner and connected it to your vehicle’s computer. This scanner will read any error messages your computer is trying to communicate with you.

Usually, the error should be displayed as a code and a short text definition. Depending on the type of the OBDII scanner, you might even get more details about expected repair costs and repair options. You also can get a better idea about whether this problem is complicated or not.

For most drivers, it's usually the basic OBDII scanner that only displays the error and the error code definition. Once you confirm that the P0171 error code is what's your vehicle suffering from, you can go ahead and test the following DIYs. 

  • Does the MAF sensor work properly? 

The first thing you need to check when dealing with the P0171 code is the MAF sensor. You need to locate this sensor by referring to your vehicle's owner’s manual and take it out carefully.

Using a certain type of MAF sensor cleaner, spray it out to clean any debris or contamination. When you are cleaning the MAF sensor to hold it vertically, the spray drops on the floor and not damaging the sensor.

After allowing the MAF sensor to dry out, reinstall it to the right location and see if the error is gone. If there are was not resolved by cleaning the MAF sensor, you need to go ahead and try the second DIY listed in the following bullet point. 

  • Does the oxygen sensor work properly? 

If cleaning the MAF sensor did not resolve your issue, check the oxygen sensor. The oxygen sensor is usually located connected to the catalytic converter. To get better guidance, you can refer to of Eagles owner’s manual.

Once locating the oxygen sensor, remove it carefully and install a new better sensor.

Usually, replacing the oxygen sensor is the 2nd common method to fix the P0171 code.

  • Clear the P0171 code 

If one of the mentioned DIY's above resolved your issue, do not expect that the P0171 code will clear itself. You must use the OBDII scanner and ask it to clear any inactive error code. 

Usually, it's also recommended that you scan the system one more time to make sure that their code was removed completely. If their code wasn't removed, then the issue was not resolved, which could mean that you performed the DIY wrong or the DIY did not resolve the issue, and there's something else hidden. 

If none of the mentioned DIY's resolve your issue, unfortunately, you won't have any other solution except going to the mechanical repair shop and have them perform manufacturer tests to determine the real culprit causing the issue. 

What tools do I need to fix a P0171 code? 

To get rid of this code, usually need to collect certain toolsets, including:

  • Pliers
  • Screwdrivers
  • Soap water 
  • Vehicles owner’s manual
  • Mass airflow cleaner
  • Fuel pressure test engage 
  • OBDII scanner 

P0171 code diagnosis mistakes 

Since the P0171 code is a very common error code a driver might face, people make a very common mistake immediately after noticing this error. This mistake is changing the oxygen sensor immediately after seeing issues with the reading.

As experts, we recommend performing a thorough inspection using an OBDII scanner and testing multiple items that might cause the problem. For instance, the easiest thing you can do is check the mass airflow sensor, and sometimes, you might need to check the vacuum leak. Therefore, never attempt to replace the oxygen sensor and think it's the final solution to eliminate the P0171 code. 

Can I drive my car with a P0171 code?

One of the very common questions we always receive about the P0171 code is how serious this code is?

This code will not specifically prevent you from driving your vehicle. However, it is never recommended to drive your car for an extended time with this error because it might introduce engine overheating and result in engine damage. Did you know that engine overheating is one of the very serious problems that you might deal with? Yes, engine overheating can result in engine self-destruction quickly if not taken care of immediately. 

How much does it cost to resolve the P0171 code?

It all depends. Based on our experience, dealing with a P0171 code might cost you somewhere between $800 and $1500. Repair costs can go extremely high if what's triggering the error code is a bad fuel injector.

If the error code is linked to an issue with the vacuum leak, it might cost you somewhere between $100 and $200? On the other hand, replacing the MAF sensor costs about $300. The fuel pump is a little more expensive and costs somewhere between $1300 and $1700. 

Issues with fuel pressure regulators require between $200 and $400. If the exhaust is the culprit, expect to pay between $100 and $200 to fix it. 

On the other hand, if you tried one of the mentioned DIY's and it resolved your issue, you will end up with 0 costs to fix the P0171 code. 

Keep in mind that labor cost is another big component when it comes to any maintenance. Did you know that performing a diagnostic only might cost you about $100? That's why we advised that every driver should have a basic OBDII scanner to at least get a better idea about what's going on with the car by knowing the error code. 


In any combustion system, there must be a certain mixture and percentage of air to fuel. If this percentage gets affected, your vehicle's overall performance will not be as it should be.

One of the very common error codes that you might deal with is a P0171 code related to having more air than fuel in the air-fuel mixture. This situation is always referred to as system running lean.

When this happens, you must immediately take care of the problem to resolve it and prevent major complications down the road.

If you realize that your car has other troubles requiring very expensive repair, it's recommended that you evaluate the situation and see whether it's the right time now To sell your car to Cash Cars Buyer or not. 

Cash Cars Buyer is one of the top-rated car removal companies in the nation that guarantees to pay you the top dollars and will provide you with free towing despite your living location around the United States. 

The best thing about Cash Cars Buyer is that our process is very straightforward and doesn't take more than a couple of days to get your vehicle removed safely and for the most money. 

To learn more about our process and our team, you can reach out to us by giving us a call at 866-924-4608 or visit our home page click on the free instant online offer.

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