P0171 OBD-II Code

If your check engine light comes on, one of the first things you can do is plug in an OBD-II scanner to read the code.

This is exactly the first step a mechanic would take if you took your car in with the check engine light on.

On the scanner, you will see a code that indicates the issue that made the check engine turn on in the first place.

One common code that comes back is P0171. We’ll take a look at what this code means and what you need to do to fix it.

What is Code P0171?

It stands for “System Too Lean (Bank 1).”

This code is related to the engine’s air-to-fuel ratio, which means that it is too lean.

In other words, there’s not enough fuel in the mix or there’s too much air. 

Symptoms & Causes

You might notice these symptoms if your car has a P0171:

  • Rough idle—It might even shake, though it depends on the severity of the issue.
  • Lack of power—Your engine won’t have the same amount of oomph that it had before.
  • Poor fuel economy—If you’re driving further than usual and getting fewer miles to the gallon, this could be a sign of P0171.

The most common causes of this code are:

  • Faulty fuel injectors.
  • Clogged air filter.
  • Vacuum leaks in intake manifold or intake hose.
  • Exhaust gas recirculation (EGR) problems.
  • Faulty oxygen sensor(s).
  • Mass airflow sensor failure.
  • Fuel pressure regulator issues.
  • Contaminated fuel system components.

Fixing the Problem

Diagnosing the cause of a P0171 can be especially difficult, and it’s something you might want to leave to your mechanic.

They will likely check sensors and run your car through a leak test which can be especially time-consuming. 

Once the issue has been identified, the mechanic will be able to recommend a course of action.

It could be something as simple as replacing an oxygen sensor or fuel filter, or it might require more complicated repairs like fixing vacuum leaks.

Regardless of what’s causing it, Code P0171 can lead to serious problems if left unaddressed. 

Cost to Fix

The cost to repair P0171 depends on the complexity of the problem.

Replacing a sensor, for example, is a relatively simple job that shouldn’t be too expensive.

However, if there’s an underlying issue like a vacuum leak or fuel pressure regulator failure, it could require more parts and labor and cost more money to fix.  

You can expect to pay anywhere between $100 to $400 to have your car repaired after a P0171 code is thrown.