Your Ford may display a P0171 code when it fails an onboard emissions test. This code indicates that the fuel system is running lean, which means more air than usual is entering the engine.
To fix this issue, you need to diagnose and repair any potential problems in your vehicle’s intake or exhaust systems.
In this article, we’ll look at the most common causes of a P0171 code in Ford vehicles and how to diagnose and fix it.
Fixing P0171 Errors with Goodhood
If you’re having trouble troubleshooting and fixing the P0171 code on your own, then you can always take your vehicle to Goodhood.
Our ASE-Certified technicians have the latest diagnostic equipment and can quickly identify the source of your Ford’s trouble.
What's the Meaning of the P0171 Code?
A Ford vehicle is equipped with a computer system that monitors the engine's performance. When this system detects an issue, it will display a code to let you know what is wrong.
The P0171 code indicates that the air-fuel mixture in your Ford’s engine is running lean. This means too much air and not enough fuel entering the combustion chamber.
Most Common Causes Why Your P0171 Code is Triggered
Now that you know what the P0171 code means, it’s time to look at some of the potential causes.
1. Vacuum Leaks
Vacuum hoses are responsible for carrying air to the intake system and must be connected securely. A leak can be caused by a cracked vacuum hose, a disconnected vacuum hose, or an intake manifold gasket leak.
2. Fuel Injector Problems
If one of your fuel injectors is blocked, leaking, or not opening properly, it can lead to a lean air-fuel mixture. A clogged fuel filter can also cause this problem.
3. Low Fuel Pressure
If your fuel pressure is lower than the manufacturer’s specifications, it could lead to a lean air-fuel mixture.
4. Mass Airflow Sensor Failure
The airflow sensor is responsible for measuring the air entering the engine. A faulty mass airflow sensor can cause your engine to run too lean.
5. Clogged Air Filter
A clogged air filter can restrict airflow, leading to a lean air-fuel mixture. If you drive in dusty or sandy areas, the air filter should be changed at least once a year or more often. Further investigation is needed if the air-fuel mixture is still running lean after you change the filter.
6. Intake Leaks
Cracks or holes in the intake manifold can cause the engine to draw too much air and insufficient fuel, resulting in a P0171 code.
7. Exhaust Leaks
Leaks in the exhaust system can cause your engine to run too lean. Your exhaust system comprises the catalytic converter, muffler, and exhaust manifold. These components should be inspected for damage.
8. Oxygen Sensor Failure
A faulty oxygen sensor can cause incorrect readings, leading to a lean air-fuel mixture. The power train control module will detect this and set the code.
9. Faulty PCV Valve
This valve is responsible for regulating the amount of air entering the intake manifold. If your PCV valve is stuck open or has failed, it can lead to a lean air-fuel mixture.
10. Unmetered Air Leaks
An unmetered air leak can cause your engine to run lean. This could be caused by a defective PCV system, a vacuum leak, or an intake manifold gasket issue.
How to Diagnose and Fix the P0171 Code?
When you see the P0171 code, it’s important to diagnose and fix the issue as soon as possible. You can do this by following these steps:
1. Check for Vacuum Leaks
Inspect all of the hoses and connections in your vehicle’s intake system to make sure there are no cracks or disconnected hoses.
2. Test Fuel Pressure
Use a fuel pressure gauge to test the fuel pressure in your vehicle and compare it to the manufacturer’s specifications. Your fuel pump may need to be replaced if the pressure is too low.
3. Check Mass Airflow Sensor
If your mass airflow sensor is dirty or faulty, it can cause the P0171 code to be triggered.
4. Inspect Air Filter
Look at the air filter and make sure it isn’t clogged or dirty.
5. Test Oxygen Sensor
Use an oxygen sensor tester to check the readings of your oxygen sensors and compare them to manufacturer’s specifications.
6. Check Intake Manifold Gaskets
Make sure all of the intake manifold gaskets are in good condition, and there are no cracks or holes in the manifold itself.
7. Test Exhaust System
Inspect the exhaust system for any cracks or leaks, and make sure all of the exhaust hangers are in good condition.
8. Replace PCV Valve
If your PCV valve is faulty, replace it with a new one to prevent further damage to your engine.
Learning how to diagnose and fix a P0171 code isn’t difficult once you know what causes it and which components can be responsible for triggering the code.
By following these steps, you should be able to troubleshoot and repair any issues that may be causing the P0171 code in your Ford vehicle.
If you think you need professional help or have any questions regarding the P0171 code in your Ford, Goodhood can help. Our certified technicians have the knowledge and experience to diagnose and fix any problem you may have.
Frequently Asked Questions
What does the P0171 code mean?
The P0171 code indicates that the air-fuel mixture in your engine is running lean, meaning too much air and not enough fuel are entering the combustion chamber.
What are some causes of a P0171 code?
The most common causes of a P0171 code are vacuum leaks, fuel injector problems, low fuel pressure, mass airflow sensor failure, clogged air filter, intake leaks, exhaust leaks, oxygen sensor failure, and faulty PCV valves.
How do I diagnose and fix a P0171 code?
To diagnose and fix a P0171 code, you should check for vacuum leaks, test fuel pressure, check the mass airflow sensor, inspect the air filter, test the oxygen sensor, check intake manifold gaskets, test the exhaust system, and replace the PCV valve.
How much does it cost to fix a P0171 code?
The cost to fix a P0171 code in a Ford vehicle will depend on the cause of the problem and can range from $50-$500.
Is it safe to drive my Ford with a P0171 code?
It is not recommended to drive with a P0171 code, as it could lead to further damage to your engine. You should diagnose and fix the issue as soon as possible. If you require professional help, Goodhood can assist you. Our certified technicians have the knowledge and experience to diagnose and fix any problem you may have.
What do I do if there's a vacuum leak?
If you find a vacuum leak, the hose or connection should be replaced. If you suspect an intake manifold gasket may be leaking, the gasket should be replaced.
What other symptoms could indicate an issue with my Ford’s fuel system?
Other symptoms that could indicate an issue with your Ford’s fuel system include poor engine performance, difficulty starting the engine, stalling and illumination of the check engine light. If you experience any of these symptoms, it’s important to diagnose and fix them as soon as possible.
How often should I change my air filter?
The air filter should be changed at least once a year or more often if you drive in dusty or sandy areas. If the air fuel mixture is still running lean after you change the filter, further investigation may be needed.
How do I know if my oxygen sensor is faulty?
You can use an oxygen sensor tester to check the readings of your oxygen sensors and compare them to the manufacturer’s specifications. If they don’t match up, the sensor may be faulty and needs to be replaced.
What is a PCV valve, and what does it do?
A PCV valve is a one-way valve that allows air in the combustion chamber to be drawn back into the intake manifold. If your PCV valve is faulty, it can lead to a lean air-fuel mixture and should be replaced.
What else could cause an unmetered air leak?
An unmetered air leak could be caused by a defective PCV system, a vacuum leak, or an intake manifold gasket issue. It’s important to inspect your vehicle for these issues and make any necessary repairs if you suspect an unmetered air leak is present.
If my check engine light is on, does that mean I have a P0171 code?
Not necessarily. If your check engine light is on, you should use an OBD-II scanner to read the trouble codes and determine if it’s a P0171 code.
What is a trouble code?
A trouble code is a diagnostic code that is assigned to an issue with your vehicle’s systems. The codes can be read using an OBD-II scanner and help you diagnose the problem. Once you have the code, you can look up what it means and figure out how to fix it.
What is a MAF sensor?
A MAF (Mass Airflow) sensor is responsible for measuring the air entering your engine. If it’s faulty, it can cause your engine to run too lean and trigger a P0171 code. Replacing the MAF sensor can help fix this issue.
What other codes are related to a P0171 code?
Other codes related to a P0171 code are P0172, P0174, and P1131. These codes indicate the same issue but with slight variations. It’s important to investigate all of these potential issues if you see any of these codes.
What are the long-term effects of running a vehicle with a P0171 code?
If your vehicle is running with a P0171 code, it could further damage your engine. It’s essential to diagnose and fix the issue as soon as possible to prevent any long-term damage.