P0171 Code (Symptoms, Causes, and How to Fix)

Is your car showing a P0171 code? This code indicates that there is too much air entering the engine’s chambers, contributing to the engine running lean.

In this article, we’ll explore the common causes of code P0171 and provide you with the knowledge you need to diagnose and fix the problem before it causes serious damage to your car.

What Does Code P0171 Mean?

A P0171 code indicates the air-fuel ratio entering your engine block is not ideal. Two main issues typically cause this code. There is either too much air or not enough fuel in the lines to create the right ratio.

When there’s too much air, you’ll often find a vacuum leak allowing an excess of oxygen into the line. Alternatively, there might not be enough fuel reaching the engine to balance the standard amount of air.

See Also: Bank 1 vs Bank 2 Location

The second scenario might indicate a problem with your fuel pump or faulty fuel injectors.

Whatever the root cause, a situation with a higher ratio of air to gasoline is referred to as the engine running lean. If there were too much fuel, the engine would be running rich.

Related: Code P0170, Code P0173, Code P0174 (System Too Lean – Bank 2)

Will a P0171 Code Clear Itself?

A P0171 code will not typically clear itself permanently without addressing the underlying issue. If the conditions that caused the code to be set are intermittent, the Check Engine Light and the code might clear temporarily, but they are likely to return if the root problem is not fixed.

Symptoms of Code P0171

Sometimes, when your check engine light comes on, you won’t notice any difference in the way your vehicle operates. When the light accompanies a P0171 code (after scanning for trouble codes), there will be other symptoms.

When there’s too much air inside, your engine cannot function as it should. When your engine is running, but you aren’t driving, you might notice a rough idle or the engine making a coughing sound.

While you drive, it may feel like your car is lacking power when you go to accelerate or drive uphill. You might even hear or feel your engine misfire.

If you don’t notice your car driving differently while showing a code P0171, then there is a chance that your sensor is faulty. These parts do fail.

However, even if there aren’t other symptoms, you must confirm that the parts around the sensor are working. You don’t want to replace an expensive part for no reason.

Causes of Code P0171

The vacuum system is the first area to check when your vehicle stores a P0171 code. A small tear or crack in the vacuum lines causes extra air to enter the system. A leak that causes diagnostic trouble code P0171 could be anywhere around the engine intake, including the PCV hoses, vacuum hoses, and the intake manifold gasket.

If all of the vacuum lines are solid, then the source likely comes from within the fuel system. A weak or failing fuel pump won’t push enough gasoline to the engine. Clogged fuel injectors or a dirty fuel filter will cause a similar backup.

In cases where the vacuum system is leak-free, there is enough gas reaching the engine, and the code P0171 still shows with your check engine light, there remains a hope of finding the cause.

The oxygen sensor, mass airflow sensor, or the air-fuel ratio sensor might be dirty, faulty, or damaged. Alternatively, there might be an exhaust leak affecting the readings.

See Also: 7 Places to Check For a Vacuum Leak

Is Code P0171 Serious?

Any time your check engine light is on, you should take the reading seriously. A P0171 code is no exception to this rule. When the engine stores this code, you should not drive your vehicle far, if at all.

When your engine runs lean, there is not enough gasoline for it to run efficiently. As a result, you run the risk of the vehicle becoming incapable of accelerating to meet the speed of traffic or to climb a steep hill. The car could also overheat and become irreparable.

Those who modify their turbocharged vehicle by increasing boost are more susceptible to get a code P0171. More air usually equals more power but you must add additional fuel to keep the ratio in line.

At best, when your vehicle shows code P0171, it is not using its fuel efficiently. You’ll waste gas and money whenever you drive.

Cost to Fix Code P0171

In this section, we’ll cover the cost of fixing code P0171 by addressing various components that might be the culprit. Remember that prices may vary based on location, labor costs, and the make and model of your vehicle.

• Vacuum/PCV Hose – Replacing a vacuum or PCV hose can range from $90 to $190, including both parts and labor. Typically, parts cost between $10 and $50, while labor costs vary from $80 to $140, based on what shop you take your car to.
• Intake Manifold Gasket – Intake manifold gasket replacement can cost you between $100 and $500. The gasket itself may range from $20 to $100, while labor costs can run anywhere from $80 to $400, again depending on your vehicle’s specifics.
• Fuel Pump – Fuel pump replacement can be pricey, with costs ranging from $300 to $800. A new fuel pump will usually set you back between $100 and $400, with labor costs falling between $200 and $400.
• Fuel Injector – Replacing a fuel injector can cost anywhere from $130 to $800, depending on your vehicle’s make and model. The injector part itself can run between $50 and $300, while labor costs can vary from $80 to $500.
• Fuel Filter – Fuel filter replacement is generally more affordable, with costs ranging from $90 to $190. You can expect the filter part to cost anywhere from $10 to $50, while labor costs will likely fall between $80 and $140.
• Oxygen Sensor – Oxygen sensor replacement can set you back anywhere from $100 to $400. The cost of the oxygen sensor itself typically falls between $20 and $200, and labor costs will usually range between $80 and $200.
• MAF Sensor – Mass Air Flow (MAF) sensor replacement costs can range from $200 to $500. The MAF sensor itself can cost you between $100 and $300, while labor costs can run anywhere from $100 to $200.
• Air/Fuel Ratio Sensor – Replacing the air/fuel ratio sensor typically costs between $130 and $500. The sensor part itself will likely fall between $50 and $300, with labor costs ranging from $80 to $200.

How to Fix

There are some straightforward diagnostic and repair steps to clear a P0171 code. If you follow the steps in the right order, you’re sure to find the problem. Clear any other codes in your car first. Then, you can begin working on this one.

First, check the vacuum system for any leaks. You can use a vacuum pressure gauge or listen around the engine for any abnormal hissing sounds.

Then, use a fuel pressure gauge to ensure that enough gasoline makes its way to the engine. Check the fuel filters and injectors during this step as well.

If there are no other problems, your last step is to run diagnostic tests to determine the health and functionality of your oxygen sensors.

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Mark Stevens

Owner at Car Treatments

Mark is a veteran auto technician who has honed his skills with over 19 years of service working at various independent shops. While Fords and Mazdas are his specialty, he enjoys working on practically any vehicle (except a Nissan 300ZX).

He’s known for his attention to detail and problem-solving skills and enjoys coming up with out-of-the box solutions when the situation requires it.

When he's not troubleshooting customers' cars, you'll most likely find him working on his current project ('96 Bronco) or cooking Italian food for his family.

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