Ford Trouble Code P0171: Troubleshooting Guide, Price, Causes, Symptoms and Solutions

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Ford Trouble Code P0171 is one of a series of diagnostic trouble codes (DTCs) that are standard powertrain codes. It is considered generic because it applies to all vehicle makes and models (1996-newer).

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Although the repair steps are more specific, they are based on a few fundamental differences based on the model and type. This Ford Trouble Code P0171 is a notification indicator that the oxygen sensor in bank 1 has detected a lean condition (too much oxygen in the exhaust).

In V6/V8/V10 engines, Bank 1 is the engine’s side with cylinder #1. P0171 is one of the most common trouble codes. This code appears because it is triggered by the first downstream (front) O2 sensor.

The sensor reads the air: fuel ratio leaving the engine cylinders, and the vehicle’s powertrain/engine control module (PCM/ECM) uses that reading and adjusts to keep the engine running at the optimal ratio of 14.7:1. If something goes wrong, and the PCM cannot maintain the 14.7:1 ratio but rather too much air, then this code will be triggered.

Therefore, this guide article discusses the problems with Ford Trouble Code P0171. Please read our article on short and long-term fuel trim to help you identify the problem and understand the engine operation solutions that can help resolve this issue.

Note: This DTC code is similar to P0174, and your vehicle may display both codes simultaneously.

Ford Trouble Code P0171: Fuel Trim System Too Lean (Bank 1)

Ford Trouble Code P0171 is set by your vehicle’s powertrain control module (PCM) when it detects that your vehicle’s air-fuel ratio is too lean. This means the PCM relays that the engine receives too much air and insufficient fuel into the combustion chamber.

The PCM receives signals from oxygen sensors in your engine bay and continuously works to adjust the right amount of air and fuel based on the readings these sensors give. When the factory-determined range is inappropriate, specifically when the fuel is lower than the motor needs, the PCM will trigger the P0171 code.

The PCM then requests that more fuel be delivered through the fuel injectors and into the engine’s combustion chamber. This action is called fuel trim, and in the case of the P0171 code, which requires more fuel, it is a positive fuel trim.

Ford Trouble Code P0171: What Else to Know

The P0171 code is set when the PCM can no longer compensate for the low fuel condition by adding fuel and will be accompanied by a check engine light. However, it is essential to note that this code is almost always paired with at least a P0170 code, as it simply states that an anomaly in the fuel trim has been detected.

The P0170 code will also be triggered if you are presented with the P0172 code, which indicates the opposite of the P0171 code. This code is triggered when the PCM detects a negative fuel trim and asks for less fuel to be pushed through the fuel injectors. This means that the engine is running “too rich.”

Another important note with Ford Trouble Code P0171 and related codes is that they distinguish between air-fuel ratio issues in Bank 1 and Bank 2. Bank 1 is the side of the engine that contains the #1 cylinder, while Bank 2 contains the #2 cylinder. However, Bank 2 is usually only found on motors such as V6, V8, or V10 and refers to the side of the engine block that contains the #2 cylinder.

Nevertheless, some in-line 4 engines are divided into Bank 1 and 2 and follow the same cylinder identification pattern.

Finally, the make and model of your vehicle will determine whether Bank 2 is on the passenger’s or driver’s side. The P0170-P0175 codes can choose precisely what fuel trim problem is occurring and where the problem is located in the engine block.

Ford Trouble Code P0171

Ford Trouble Code P0171 Diagnostic Theory

If the vehicle has the P0171 error code, the computer can no longer adjust the air and fuel mixture automatically. The P0171 code applies to 4-cylinder (Bank 1) engines as they generally only have one bank. If you have a V6 or V8 engine, you may also get a P0174 code, which refers to Bank 2.

When the code states that the fuel system is “too lean,” the computer has added more fuel, called Long-Term Fuel Trim. Ideally, the Long-Term Fuel Trim should be close to 1 to 2 percent.

When code P0171 is assigned, the Fuel Trim is compensated between 15 percent and 35 percent. When this happens, the computer recognizes an improper condition in the Fuel System control.

The first step in diagnosing the Ford Trouble Code P0171 code is to look at at least three ranges of Long Term Fuel Trim numbers on the scanner. Check the idle reading of 3000 RPM with no load and 3000 RPM with at least 50 percent load.

Then, check the freeze frame information for the code to see which range failed and the operating conditions.

What Does The P0171 Code Mean

Code P0171 or system too lean bank 1 means too much oxygen or too little fuel in the exhaust. It is a ‘lean’ condition or ‘low fuel trim’ code.

The Ford Trouble Code P0171 OBD-II code indicates that the fuel system on the first edge of the engine is weak or there is a vacuum leak near this side of the engine. The lean state occurs when the engine receives too little or too much fuel.

Why is Code P0171 and Running “Too Lean” Important

Cars and light trucks that run “lean” are highly polluting vehicles. Most of the toxic NOx pollution that can cause asthma is caused by vehicles running too lean. Cars running lean can also misfire, which results in raw fuel (HCs) being introduced into the catalytic converter, causing internal damage and releasing into the atmosphere.

When behind a stalled car or truck, it can be eye-aching. In comparison, an engine running “rich” (that does not misfire) does not smell (CO is odorless), or you may smell rotten eggs, which is sulfur dioxide produced by the Catalytic Converter.

Ford Trouble Code P0171 is not an Oxygen Sensor problem. Before the P0171 code is possible, the computer runs a series of tests to validate the reading from the oxygen sensor. Since the oxygen sensor passed the readiness test and did not set any codes, the computer then looked at the Fuel Trim adjustment. When the computer determines the air-fuel mixture is too lean, it sets the P0171 code.

Main Causes of Ford Trouble Code P0171

The most common cause of code P0171 – and codes P0170 and P0173-P0174 – is unmeasured air entering the combustion system. Often, this happens due to a faulty or dirty mass airflow sensor or a weak fuel pump.

You may also find that a stuck or uncleaned fuel filter or fuel injector can cause unmeasured air to enter the system and trigger one of the following codes to be set. A faulty oxygen sensor should also be considered a cause of a lean or rich engine. Exhaust leaks can also be the cause of P0171 and related codes being set in your car.

However, it is essential to distinguish that for codes P0172 and P0175, whose problem lies in the engine running too rich on the Bank 1 or Bank 2 side of the engine block, the most common cause is fuel injector malfunction. If the fuel injector is damaged, it leaks and pushes too much fuel into the chamber. Leaks in the fuel lines can also make the fuel injectors appear to be functioning correctly.

However, if the fuel lines operate within factory-set conditions, you may find leaks in the vacuum lines that allow additional oxygen to escape before it mixes with the fuel. This will always cause the engine to run too rich, and you will lose mileage or power.

How Serious is Ford Trouble Code P0171

Of course, Ford Trouble Code P0171 and its related codes vary in seriousness. The code itself does not pose any immediate danger, but you should have it checked by a qualified technician immediately. If the code is present and extended in the PCM, it may cause further damage, requiring more expensive repairs.

As we have pointed out, even if there are no immediate symptoms, the vehicle may run too rich and damage fuel efficiency. If your fuel pump or injectors are damaged, long-term damage can occur if the wrong air-fuel ratio is constantly fed into the system. The factory-set engine operating conditions exist for a reason, namely because the ratio has been tested and is necessary to keep the vehicle running smoothly for longer.

Nevertheless, most cars today will take corrective measures to avoid severe damage to the engine by going into limp mode or reduced power mode. As we have noted before, running a vehicle in lean can cause pinging or sparks, which can have more dangerous consequences.

Pinging means that Oxygen (O2) is converted into Nitric Oxide (NOx), an atmospheric pollutant. This process can cause your combustion chamber to malfunction and damage the valve surfaces. It also causes the catalytic converter to overheat to the point where it burns very hot and can cause other car parts to catch fire.

What are the Common Causes of P0171 Codes

Always check to ensure that no PCM software updates are scheduled or available. As the vehicle engine often wears out, the PCM Fuel Map software inaccurately compensates for this condition. The fuel mixture becomes lean, and eventually, the code is set.

Vacuum leaks are widespread. The cause could be a torn PCV hose, a torn Intake Air Boot, or even a broken seal on the dipstick (the dipstick is part of the PCV system, and if it is not sealed, too much-unmeasured air will enter the engine).

There may be a sticky/leaking EGR Valve or an EGR or Intake Manifold Gasket. If it’s a V6 or V8 engine and the code is only on one side/bank, it could be a damaged Intake Manifold Gasket or a cracked/leaking manifold.

What If There is No Vacuum Leak and Code P0171 is Set

A Bulk Airflow Sensor that is “being reported” can commonly cause the Ford Trouble Code P0171. This means that the Airflow Sensor tells the computer that less air is entering the engine than it is.

The oxygen sensor tells the computer that more fuel is needed because the bulk airflow sensor still says there is too little air, and the oxygen sensor reports that the mixture is still too lean.

The computer tries to compensate, but since resolution is impossible, it sets the code. It is essential to state that the Oxygen Sensor is accurate and that the fuel mixture is too lean. In this case, the airflow meter or sensor does not accurately report the actual amount of air entering the engine.

How Do I Know If the Problem is the Bulk Airflow Sensor

There is an efficient “truth test” for any Bulk Airflow Sensor. Start the engine, let it idle, and then check the Barometric Pressure reading on the scan tool data. If the reading is around 26.5 Hg and you are close to sea level, you know that your Air Flow Meter is faulty because it tells you you are about 4500 feet above sea level.

When the Bulk Airflow Sensor sees this Barometric reading, it will adjust its Air Density table and “report” the actual amount of air entering the engine. This happens because the Barometric Pressure Sensor is part of the Bulk Airflow Sensor.

Sometimes, the Airflow Sensor and sensing wires are covered in dirt, dust, or oil residue, which can also set P0171. Cleaning the sensor may delay the problem, but the MAF sensor must eventually be replaced.

Keep the Air Filter and cover free from dirt, dust, and oil. Cleaning and replacing the filter and cover as needed will prevent new MAF failures.

Is it OK to drive with code P0171

Codes that appear, such as the P0171 lean fuel trim, pose performance issues that can result in costly damage. These issues may range from low fuel economy poor engine performance, to internal engine damage.

In addition, if this code is stored for a long time, your car’s catalytic converter could be damaged. Catalytic converters are costly to replace. Therefore, it is best to avoid driving with P017.

What Causes the Ford Trouble Code P0171

The Ford Trouble Code P0171 code may mean that one or more of the following has occurred; some possible causes of the P0171 engine code are

  1. A vacuum leak
  2. Possible cracks in the vacuum or PCV lines/joints
  3. Damaged or jammed open PCV valve
  4. Weak fuel pump
  5. The fuel pressure regulator was damaged
  6. Clogged fuel filter
  7. The powertrain control module was damaged
  8. Fuel injector stuck/unplugged or damaged
  9. Low fuel pressure (possibly clogged/dirty fuel filter!)
  10. Oxygen sensor faulty
  11. Exhaust gas leak between engine and first oxygen sensor
  12. MAF (Mass Air Flow) sensor is dirty or faulty
  13. Oxygen sensor failed or damaged (bank 1, sensor 1)
  14. Catalytic converter clogged
  15. Problem with mass air flow sensor

What are The Common Symptoms of The Ford Trouble Code P0171

A common symptom of Ford Trouble Code P0171 and codes P0170 and P0173-P0174 is that the engine will appear to run with a lack of power and may stall at any time. The stalling usually occurs when you stop at a traffic light, and the engine can no longer maintain a steady idle condition.

However, if a vacuum leak causes the problem, you may hear a hissing sound from the engine bay. Your engine may have difficulty revving because it is not receiving the right amount of fuel in the combustion chamber. You may also hear a knocking or engine noise when loading or accelerating on an incline and a loss of power as less fuel is channeled to the right place.

As for codes P0172 and P0175, when the engine is running too rich, you may experience fewer physical symptoms. This happens because more fuel is being delivered to the engine, and your vehicle runs inefficiently due to the extra fuel being burned. You will receive fewer miles per gallon and have to refuel more often.

However, sometimes, you may notice physical symptoms if the air-to-fuel ratio is too high. Black smoke or residue may come from your vehicle’s exhaust system. You may also experience other issues, such as misfiring on one of the engine cylinders, and you will feel a rough idle or lack of power.

Symptoms of the P0171 code include:

  1. Check if the Engine Light is on or flashing.
  2. Performance issues, such as lack of power on acceleration and multiple “coughs” or misfires
  3. Loss of power
  4. Roughness at idle
  5. Engine misfires or “coughs”.
  6. Spark plug tips are white
  7. Control module software needs to be updated
  8. Vacuum leaks (intake manifold gaskets, vacuum hoses, PCV hoses, etc.)
  9. Air mass flow sensor
  10. Clogged fuel filter or weak fuel pump
  11. Clogged or dirty fuel injectors

Common Diagnosis Faults for code P0171

  • Oxygen sensor

Pollutant Gas Expelled

  • NOX (Oxides of Nitrogen): One of two materials that, when exposed to sunlight, can cause smog.
  • HCs (Hydrocarbons): Droplets of unburned raw fuel that create odours, affect breathing, and contribute to smog.

Ford Trouble Code P0171: Common Errors in Diagnosis

A common mistake is not looking at the technical service bulletin for your specific car model, which may be relevant to this issue.

While not all trouble codes are associated with technical service bulletins, it’s worth double-checking. They can save you a lot of time and work.

Ford Trouble Code P0171 Additional Causes

A plugged Fuel Filter or a malfunctioning Fuel Pump can cause the Ford Trouble Code P0171. The computer hears (accurately) from the Oxygen Sensor that the Fuel Mixture is too low, so it keeps increasing the fuel delivered to the combustion chamber.

However, the fuel system cannot increase the fuel used.

If you still need help finding the problem, verify that the fuel pressure and delivery are within specifications. If the fuel pressure and volume are OK, check the injectors and perform an injector drop and flow test to see if they can deliver enough fuel.

Dirty/contaminated gas can clog the injectors and trigger this lean code.

Will the P0171 code go away by itself?

It most likely won’t. If you see this code, you should have it checked as soon as possible.

Can a dirty air filter cause the P0171 code?

If your car’s air filter is clogged or dirty, airflow will be obstructed or restricted, resulting in a lean running state. A dirty or damaged MAF sensor or a clogged fuel filter can also cause the Ford Trouble Code P0171.

Can a faulty spark plug cause P0171

Very unlikely. A vacuum leak downstream of the MAF sensor or a faulty MAF sensor are the most common causes of code P0171 (too lean, Bank 1).

Can a faulty PCV valve cause P0171?

Yes, Vacuum or inlet leaks, low fuel pressure, faulty PCV valves, or faulty MAF sensors are the most common causes of the P0171 code. However, other factors can potentially contribute to the P0171 error code.

Can a bad O2 sensor cause P0171

The problem may not be a faulty O2 sensor but relatively low fuel pressure, engine vacuum leaks, or dirty fuel injectors that cause the engine to run lean.

Can a faulty fuel cap cause a P0171 code

It does not set a false code. Ford Trouble Code P0171 is a lean code caused by a vacuum leak, mass airflow failure, faulty PCV valve, or low fuel pressure.

What Causes Ford Trouble Code P0171

A dirty mass airflow (MAF) sensor is one of the most common causes of Ford Trouble Code P0171 and P0174 lean codes. Dirt can stick to the MAF sensor wires and form a coating, thus slowing down the sensor’s reaction to airflow variations.

Fuel vapours returning through the intake manifold and throttle body after engine shutdown can also contaminate the MAF sensor. The vapours can cover the sensor wires with a layer of wax.

As a result, the MAF sensor reports insufficient airflow, causing the powertrain control module (PCM) to inject insufficient fuel to maintain the correct air/fuel ratio balance. Your Ford engine becomes lean and generates a P0171 or P0174 code.

Can P0171 Cause Overheating?

Yes. Your car’s engine will not maintain the proper air-fuel ratio as the P0171 code activates due to fuel delivery system failure. This can lead to fuel wastage and poor fuel economy.

Another problem is low engine speed. The engine damage is irreparable as your car continues to overheat.

Can a bad fuel injector cause P0171?

The Ford Trouble Code P0171 is associated with your car experiencing fuel injector blockage, which implies that the engine controller senses a lean state. If injectors leak or are not atomizing correctly, you may also see an error code for a prosperous state.

Can an exhaust leak cause P0171?

Vacuum leaks are a possible cause of the check engine light coming on in cars with P0171 and P0174 codes stored in the PCM. The codes are activated when the PCM detects excess oxygen in the exhaust.

Can P0171 cause a misfire?

The codes should ideally result in the engine running poorly, which the driver would see as high idle, stalling, loss of power, or even engine stalling. All this can happen even before the check engine light comes on.

What do P0171 and Po174 Mean

Code P0171 indicates Bank 1 of the engine has a lean fuel mixture. P0174 indicates Bank 2 of the engine has a lean fuel mixture. Engine Bank 1 is on the same side of the engine as Engine Cylinder 1. Engine Bank 2 is on the opposite side of the engine.

An ignition sequence and cylinder location diagram may be needed to see which side of the engine is in Bank 1 or Bank 2. P0171 is triggered by the “upstream” engine bank 1 oxygen sensor, and P0174 is triggered by the “upstream” engine bank 2 oxygen sensor. The oxygen sensor alerts your system when conditions are too light, which means there is too much oxygen in the exhaust. The symptoms and causes will help you determine the real problem and how to fix it.

Your bank 1 or 2 sensors will be called “sensor 1” or “sensor 2.” Sensor 1 refers to the “upstream” sensor near the engine and before the catalytic converter. Sensor 2 is “downstream,” or after the converter. This upstream sensor verifies the correct air/fuel ratio entering the engine cylinders by measuring the oxygen level in the exhaust gas exiting the cylinders.

It does this by signaling a continuous but changing voltage to the computer. A constant high voltage reading indicates a rich fuel mixture but insufficient oxygen. A persistently low voltage reading indicates a lean fuel mixture and too much oxygen.

The optimal ratio is 14.7:1 (air: fuel). When your powertrain/engine control module receives a reading indicating too much oxygen and the incorrect ratio, it sends error codes P0171 or P0174. Depending on the problem, it may send both codes if the problem is causing a lean condition on both engine banks.

It’s important to note here the nature of the oxygen sensor sends these codes, with no other oxygen sensor failure codes telling us that the sensor is functioning as it should. This code is tricky because if it presents itself, NO monitored component has failed or would also get a code. In short, the engine is running lean, but the computer can’t figure out why.

Symptoms: P0171 and P0174

In many cases, engine performance issues are not noticeable. However, some lean situations may cause your vehicle to experience the following performance issues:

  • Surging or hesitant acceleration
  • Misfires (which will usually result in a misfire code)
  • Spark knock or detonation
  • Reduced power
  • Rough idling

Generally, you will only be warned by the presence of a lit CEL. Look for one of these common causes to determine how to resolve the trouble code.

The first thing to determine is what other codes are present. If one of the codes arrives (or both) simultaneously, such as the Mass Airflow Sensor code, then it’s logical to assume that the MAF sensor may be causing the lean condition.

If P0171 or P0174 presents itself or both codes are stored, you have a problem that requires more detective work. It would be best to look beyond the engine computer monitors’ sensors and items.

Common Causes: Ford Trouble Code P0171

Many small or large repairs can cause this problem. Please start with the most straightforward problem and work through it to identify the code causing your problem. Lean conditions are often caused by air entering the system somewhere that cannot be monitored. The two main areas for this are the intake system, usually after the MAF sensor, or a vacuum leak somewhere in the intake.

Start by checking the intake boot from the MAF to the throttle body. Check for cracks, loose hose clamps, or places where air is getting in. Next, check the entire vacuum hose on the engine for cracks or breaks in the hose. When the engine is running, listen carefully, as you can often hear a large vacuum leak from the sound of air being sucked through a crack. Also, check the entire PCV hose system for leaks or cracks.

If nothing shows up here, other significant problems may occur. One is a vacuum leak due to failure of the intake manifold or throttle body gasket. This will cause a large vacuum leak and trigger a lean condition.

Another possible issue is improper refueling, which can be caused by low fuel pressure (possibly a clogged fuel pressure regulator, pump filter in the tank, or weak pump) or weak/clogged/misfiring fuel injectors. It’s important to note that fuel issues like these often trigger misfire codes, either randomly or on specific cylinders.

Ford Trouble Code P0171: Possible solutions

Clean the MAF sensor. If you need help locating it, consult your service manual. Remove it and spray it with an electronic cleaner or brake cleaner. Be careful not to damage the sensor, and ensure it’s dry before reassembling it.

  1. Check all vacuum and PCV hoses, replace/repair as needed
  2. Check all hoses and connections on the air intake system
  3. Check and leak test the intake manifold gaskets
  4. Check for dirty fuel filters and proper fuel pressure
  5. You will want to monitor short- and long-term fuel trims using an advanced scan tool.
  6. If you have access, you should run a smoke test.

How to fix the P0171 Code

You can usually fix Ford Trouble Code P0171 using the following steps:

  1. Replace the fuel pump or fuel filter
  2. Replace the fuel pressure regulator
  3. Replace the powertrain control module
  4. Replace one or more injectors
  5. Replace one or more oxygen sensors
  6. Replace the mass air flow sensor
  7. Repair vacuum leaks

How to Fix P0171 and P0174

Another option when thoroughly checking the intake boot is to stop at the MAF sensor itself. The MAF sensor can become dirty or oily and send out false signals, usually indicated by MAF trouble codes.

This is especially true if you use an oiled air filter containing too much oil, which can cause contaminants to stick to your MAF sensor. Once you have located your sensor, you can remove and clean it with an MAF cleaning spray.

Once the sensor is cleaned and working correctly, and all hoses and inlets have been checked, the next step is a vacuum test on the engine while running. A vacuum diagnostic gauge can be fitted and used, or a professional shop can help. If the vacuum is out of parameters or fluctuates wildly, there may be hidden damage to the hoses, or the intake manifold gasket is suspect.

Once you have found the solution and repaired or replaced the appropriate component, check your vacuum cleaner and reset the trouble code to test whether you have fixed the problem or need to look for further leaks.

How Easy is it to Diagnose Code P0171?

People wonder what is wrong with the vehicle. The most common mistake made when diagnosing Ford Trouble Code P0171 or other related codes is to immediately replace the air-to-fuel sensor or oxygen sensor and move on. As long as you are equipped with a sophisticated OBD-II scanner, you should be able to determine precisely where the air/fuel condition occurs, and then you can check the related parts.

Mass airflow sensors or vacuum leaks should be prioritized when diagnosing related codes, as they are often the source of unmeasured air entering the combustion chamber. Reading and analyzing the fuel trim data and freeze frame is essential to diagnose P0171 or other related codes properly.

Unfortunately, it is easy for someone with little experience to misdiagnose a problem like this. A common fix is to replace the air-fuel sensor or O2 sensor. However, replacing these parts may not solve the root of the problem, as the code could be caused by a dirty or damaged mass airflow sensor or even a vacuum leak. To compensate for this, the new O2 sensor may be forced to read differently.

Reading and analyzing the fuel trim data and freeze frame is essential to properly diagnose the Ford Trouble Code P0171 issue. Again, this is best left to a qualified technician with experience dealing with these issues.

How Difficult is it to Check Code P0171?

We recommend contacting professional help as the following is for informational purposes only.

The first step to diagnosing and fixing Ford Trouble Code P0171 or any other related code is to leave this part of the process to a qualified technician to resolve any issues with the fuel system. They will want to ensure that the fuel pressure and injector pulsations are where they should be and that the fuel injectors are functioning correctly and are not clogged.

They will also check your fuel lines for damage, followed by your vacuum lines, to see if there are any leaks. They should fix any issues, as these leaks cause air to escape instead of entering the engine’s combustion chamber. Again, while an educated car enthusiast can repair this, there is still much room for error; therefore, an experienced, trained technician should do this.

The next step is to remove and clean the mass airflow sensor before reconnecting it. A qualified technician best does steps like this, which should be done by someone other than DIY enthusiasts. Once reconnected, you should rerun the diagnostic test to see if code P0171 or its related code is displayed.

Finally, you should check for exhaust leaks and repair the system with professional help. If the problem persists, consider replacing the air-to-fuel and oxygen sensors to fix the issue.

How does your mechanic diagnose the P0171 code

Without any other fault codes, mechanics can diagnose Ford Trouble Code P0171 using a vacuum gauge to check for engine suction leaks.

  1. A vacuum leak will produce a hissing sound, usually only heard when the engine is turned off.
  2. A fuel pressure gauge also checks the fuel pressure sensor and MAF (mass air flow) sensor.
  3. Engine vacuum and fuel pressure must be within the manufacturer’s standards to maintain the correct air/fuel ratio. Therefore, these two checks will determine the source of this error code.
  4. If the cause is still unknown after the mechanic has performed these two checks, the problem is most likely with the sensor.
  5. The mechanic will then use the manufacturer’s techniques to test the bulk airflow and oxygen sensors.
  6. If all these tests are completed and no problems are detected, the problem is most likely with the powertrain control module.

Need Additional Help with Your P0171 Code?

You certainly don’t want to risk the P0171 or other related codes causing permanent damage to your car. More than anything, the issue of how your engine burns fuel and air should be prioritized. The more you wait for an issue like this, the more likely you’ll fix some more expensive repairs.

For more information on the Ford Trouble Code P0171 and all related codes or to find a qualified technician to help you address these issues, contact a service center and get your car safely back on the road in no time.

Ford Trouble Code P0171 Price

How much does it cost to fix the P0171 code?

When you take your car to a repair shop for diagnosis, most will start with an hour of work to diagnose your specific problem. Depending on the shop’s labour rates, this usually costs between $80 and $150.

Then, if you ask them to make repairs, many, if not most, businesses will apply this diagnosis fee to any required repairs. A shop will then be able to give you an accurate price quote for fixing your P0171 problem.

Repair Estimate for P0171

One or more of the following repairs may be required to address the underlying issue of error number P0171. The estimated cost of each repair includes the cost of related parts and the cost of labour needed to complete the repair.

  1. Vacuum leak repair: $100-$200
  2. MAF replacement: $300.
  3. Fuel pump: $1300-$1700
  4. Fuel pressure regulator: $200-$400
  5. Exhaust repair: $100 to $200 (if welded for repair)
  6. Oxygen sensor: $200-$300

FAQs: People also ask for Ford Trouble Code P0171

Q: How do you fix the code P0171?


  1. Change out the fuel pump and fuel filter.
  2. Replace a faulty mass airflow sensor.
  3. Install a new fuel pressure regulator.
  4. Upgrade from your existing fuel injector.
  5. Seal off a vacuum leak.

Q: What is the most common cause of the code P0171?

A: Yes, Vacuum or intake leaks, low fuel pressure, a defective PCV valve, or a faulty MAF sensor are the most typical reasons for the P0171 code.

Q: Which oxygen sensor is responsible for P0171?

A: P0171 is triggered by the engine bank 1 “upstream” oxygen sensor, and P0174 is triggered by the engine bank 2 “upstream” oxygen sensor. The oxygen sensor alerts your system when the condition is too low, meaning there’s too much oxygen in the exhaust.