Ford P0171– Meaning, Causes, Symptoms, & Fixes

Understanding each code in your car can save you a lot of stress. Each code carries a meaning that could indicate whether the issue at hand is severe. For instance, let’s assume that you enter your Ford one morning, and instead of coming on, it fails. When you use your OBD II to scan the problem, code P0171 is displayed. Many thoughts will run through your mind, like, what is this code? What does it mean? How can I resolve it? The bad news arises when you don’t have the scan tool because you can’t quickly identify what it is. Fortunately, this article will explain everything you need to know about code P0171 in your Ford.

 What does code P0171 mean?
Code P0171 means that the Power Control Module (PCM) has detected a lean state in the engine. The engine can become lean when an air-fuel ratio imbalance occurs in the combustion chamber. For the engine to function correctly, the air-fuel mixture ratio should be 14.7:1. A deviation from that will trigger code P0171 in your Ford. Such variation can be due to a leaking vacuum which allows more air into the combustion chamber, or a defective fuel system that deprives the combustion chamber of enough fuel.

What are the symptoms of code P0171 in your Ford?

There are many symptoms associated with code P0171 in your Ford Vehicle. They include the following:

 1. Illuminated check engine light

 Since code P0171 is caused by an issue with the engine’s combustion chamber, you will mostly notice that the check engine light comes on in your Ford dashboard. However, since the check engine indicates many issues that may not be related to the combustion chamber, it does not guarantee that code p0171 will be thrown. The good thing about the check engine light is that it illuminates in various ways depending on how severe the issue is. For example, a check engine light that comes on severally indicates a critical problem.

 2. Engine misfires

An optimal air-fuel mixture and enough spark plugs must be ensured for the combustion chamber to ignite. Failure to do so will result in an engine misfire. An engine misfire can cause problems such as poor fuel economy and engine failure. So, it would be best if you found out its cause immediately. Since what’s causing it is associated with the engine, you will notice code P0171 in your Ford.

3. Loss of Power

Your Ford vehicle relies on the power from the engine to move. This power is created through the combustion process in the engine. If the engine is deprived of enough fuel or air, limited or no power is produced. Luckily, you can quickly notice when your engine is losing power. In particular, your engine is losing power if you are pressing hard on the accelerator and not seeing a sufficient change in speed.

4. Rough Idle

Defective spark plugs can cause a rough idle. If the spark plugs cannot ignite to produce enough sparks, the combustion in the engine will be affected. As such, if you notice that your car is shaking or making odd sounds while idling, there is a high chance that code P0171 will be shown in the OBD II device.

  5. White deposits on the tip of spark plugs

If the spark plug tip has white deposits, your Ford will likely have the error code P0171. These white substances indicate that the spark plugs are burned. Burned spark plugs will not produce enough sparks, resulting in an exceeded air-fuel mixture ratio.

Can you drive when there is code P0171?

 If the lean condition is not severe yet, you will not observe a significant difference in your Ford’s performance. In that case, you can continue using the car until you get time to resolve what is causing it. However, if most of those symptoms start showing up, extended driving can cause severe damage to the engine or its major components. Since most of the engine’s parts are expensive to repair or replace, avoiding using the car once you identify code P0171 may be the better option.

What causes code P0171?

 An issue with any parts that make up the fuel system can cause a P0171 code in your Ford. You should check the following parts when the code is shown in the OBD II system.

 1. Parts responsible for creating a vacuum in the engine

The engine vacuum is responsible for pulling air into the cylinder, creating an optimal air-mixture ratio. Vacuum is the difference between the pressure in the intake manifold and the atmospheric pressure. As such, if the parts that work together to create it get damaged, the vacuum will leak, resulting in air loss to the atmosphere. Such components include the hoses, the intake manifold gasket, the boost pipe, etc.

2. Fuel Pump

 Code P0171 can be caused by an issue with the fuel pump. The fuel pump creates the pressure needed to pump the fuel from the fuel tank to the engine. Therefore, low fuel pressure will be supplied if the fuel pump gets damaged. Consequently, the fuel that reaches the cylinder will be low, resulting in a lean combustion chamber.

 3. Purge valve

The purge valve is one of the critical parts in your Ford’s evaporative emission system (EVAP). It prevents fuel vapor from escaping into the atmosphere, hence preventing a lean situation in the engine. This valve opens and closes depending on the signals received from the PCM. But sometimes, it gets stuck open, allowing the vapor to escape from the fuel tank. That will result in the check engine light coming on and code P0171 being thrown.

 4. Oxygen(O2) sensor

Your Ford’s engine does not need any air to function. It needs air with sufficient oxygen in it. As such, there is a sensor in the engine called the oxygen sensor. This sensor monitors how much oxygen is in the unburned air that exits the engine through the exhaust system. By doing so, the amount of oxygen in the air-fuel mixture is known. If too little oxygen is in the mixture, the PCM will electronically cause the intake valves to open. This will allow more oxygen into the cylinder. When the oxygen sensor malfunctions, code P0171 will be shown since the PCM will not detect such a lean situation.

 5. Mass airflow sensor (MAS)

The MAS is a critical sensor between the intake manifold and the air filter. It measures the volume of air entering the engine and sends the readings to the PCM. The PCM will, in turn, use the readings to determine the amount of fuel to be injected into the combustion chamber. So, if this air sensor gets faulty, no readings will be sent to the PCM resulting in code P0171 being exhibited.

6. Fuel Injector

As the name suggests, the fuel injector is responsible for injecting fuel into the engine’s combustion chamber. But before doing so, it turns it into mist which can quickly burn in the cylinder. That being the case, if it gets clogged or damaged, little or no fuel will be introduced into the chamber. This will make the chamber lean, resulting in code P0171.

7. Sensor wiring

The sensors in the engine rely on electric current to send signals to the PCM. If the wirings get faulty, the PCM will not be notified when the combustion chamber gets lean. This will result in code P0171 being indicated in the OBD II system.

 8. Fuel filter

 A fuel filter prevents foreign substances, such as dust and debris in fuel, from reaching the combustion chamber. Such particles will lower the fuel pressure leading to a bad ratio of air and fuel in the combustion chamber. Therefore, if the fuel filter is faulty, it will fail to screen those particles; hence code P0171 will appear on the OBD II system.

 9. The PCM

 If all the above parts are in good condition, the PCM could be the one causing code P0171 in your Ford. It is rare for the PCM to malfunction. But since it is a computer, it can encounter bugs that wrongly indicate code P0171.

How can you fix code P0171?

 The first step when fixing the Ford P0171 code is to identify its exact cause. With the right tools, you can do so within an hour. The tools you need to accomplish the task are the OBD II system, FIXD sensor and app. These tools will give you live data that will enable you to diagnose and fix each specific issue quickly. However, these tools may be expensive; hence you may want to visit a mechanic shop for a diagnosis. That will cost you around $75 to $150.

 Once you have identified the issues causing it, you can solve them. But if you don’t have the skills and time to do so, you can also ask the shop to do it. Depending on the affected part, the cost of fixing code P0171 will range between $100 to $1700. Below are the fixes which you can undertake.

 1. Fix the vacuum leak

If the vacuum leak is responsible for code P0171, you can eradicate the code by repairing or replacing the part causing the leak. One way of identifying a vacuum leak is by spraying water on those parts. If one of the parts sucks in water, that is the part causing the leak. Depending on the extent of the damage, you can choose to either repair or replace it.

 2. Replace the fuel pump

 The best thing to do when the fuel pump gets damaged is to replace it. This is because repairing it may only partially fix its problem. Since replacing it requires that specific steps are followed keenly, the best option will be to take your car to a specialist.

 3. Replace the Oxygen sensor

A bad oxygen sensor cannot be repaired due to the complexity of its parts. Hence, the only way to get rid of code P0171 is by replacing it.

 4. Unstuck the purge valve

The purge valve can stay stuck open when the wiring connection is faulty. If the wiring is shorted, the PCM won’t be able to close it electronically. So, by replacing the wires, you can resolve Ford P0171 code.

 5. Replace the Mass Airflow Sensor (MAS)

 Like the oxygen sensor, it is hard to repair the MAS. So, the only option is to replace it with a new one. Fortunately, the process of replacing it is quick and easy. You only have to unscrew the bolts holding it to the engine and install the new one.

 6. Clean the fuel injector

 A clogged fuel injector can be cleaned using a kit that contains polyetheramine (PEA) fluid. The process is pretty simple since the kit will give you directions on how to do so. Your car’s manual will also tell you how to locate the fuel injector. However, if the fuel injector is damaged, you will have to install a new one since it cannot be repaired.

 7. Fix the sensor wiring

If the sensor wirings are lousy, replacing the cables will erase Ford P0171 code. Your car’s manual should also tell you where the sensor cables are located and how to access them.

 8. Replace the fuel filter

 Is the fuel filter damaged? Replace it to solve the error code. The process won’t take you more than twenty minutes as it is straightforward to do it.

 8. Reboot the PCM

 If the diagnosis fails to identify what is causing the error code, the PCM might be responsible. Luckily, an issue with the PCM can be solved by rebooting it. You can also find the instructions on resetting it in your Ford manual.

To sum up

Getting a P0171 error code in your Ford shouldn’t ruin your day. This is because it rarely indicates that something is damaged severely in your car. However, that doesn’t mean you should avoid examining what’s causing it. Ford P0171 can be caused by issues with the fuel pump, fuel filter, oxygen sensor, fuel injector, purge valve etc. These are critical components in the engine; hence if they are allowed to deteriorate further, they can ultimately damage the engine. Therefore, when you get the code, follow the above steps to resolve it immediately and stand a chance to avoid incurring a substantial repair cost.

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