Getting a diagnostic code on your vehicle can be concerning, but you can identify the reason for a trouble code and, in some cases, prevent these warnings from popping up in the first place.

You may have seen the P0171 code from your vehicle. Here’s what you need to know about this message and how you can resolve the issue.

What Is the P0171 Code?

Code P0171 relates to the first bank of an engine. The code indicates that the air-to-fuel ratio is running too lean — something that can happen for various reasons. To see the P0171 code, you’ll need a diagnostic scanner. Otherwise, you’ll see a check engine light illuminating the instrument cluster.

 

What Does the P0171 Trouble Code Mean?

Code P0171 surfaces when there is not enough air or a lack of fuel making its way to the engine. An air-to-fuel ratio that runs too lean makes your vehicle lose power. You may notice your car, truck or SUV stalling or idling roughly as well.

Several sensors regulate the air and fuel mixture inside your vehicle. Most often, P0171 codes occur after a leak or electrical problem.

 

Possible Causes of the P0171 Code

Your vehicle may get the P0171 code due to dirty sensors or a faulty fuel pump. Specifically, mass airflow sensors are known to trigger this error code, as this connection is responsible for measuring the amount of air reaching the engine.

Clogged fuel filters are another common culprit that often creates this code. When working properly, your car’s fuel filter brings a steady stream of fuel to the fuel injectors. When fuel filters are left unchanged after driving thousands of miles, the fuel injectors may allow unmetered air to interfere with the fuel mixture.

The P0171 code calls for troubleshooting. Your check engine light may turn on due to these factors, too:

• The oxygen sensors on your vehicle stop working.
• There is a vacuum leak somewhere in your fuel system.
• The powertrain control module fails.
• Your vehicle’s fuel pressure regulator needs replacement.

 

Symptoms of Code P0171

You should be able to tell something is off with your vehicle before you or a mechanic runs a diagnostic test via the OBD-II port. The most significant warning sign that your engine’s Bank 1 system is running too lean is a noticeable loss of power. This issue manifests when you press the acceleration pedal because your vehicle may have a hard time increasing speed.

Most P0171 code indicators relate to your engine’s performance and reliability. You may find your car, truck or SUV has trouble starting or that your engine hesitates to upshift and downshift. In serious cases, your automobile’s catalytic converter can stop functioning correctly when you ignore the P0171 code for an extended period.

 

How to Diagnose Code P0171

It’s vital to perform an OBD-II scan of your vehicle before assuming the issue’s cause. You or a mechanic should scan for Code P0171 to ensure this is the correct diagnosis for your automobile and that no other fault codes are showing up upon seeing a check engine light.

You might think that changing out some sensors will resolve the issue, but a proper OBD-II scan will confirm the problem takes place around Bank 1. It is recommended that someone with experience in the diagnostics field check for Code P0171. A professional mechanic should have some additional tools to get to the bottom of the issue.

Below is a list of areas to inspect after finding Code P0171. Complete these steps in the order until you uncover the reason for the error message:

1. Use a vacuum gauge to locate leaks —only when the engine is off.
2. Check fuel sensor and mass flow air sensor performance with a fuel pressure gauge.
3. Follow manufacturer instructions for testing oxygen sensors throughout the fuel system.
4. Once you’ve tried all other options, the problem likely lies in the power control module.

 

How Do I Fix the P0171 Code?

You can resolve the Bank 1 system running too lean error using a few approaches. Depending on the issue’s cause, you may be able to turn the check engine light off by completing one or more of these repairs:

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

 

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