What Are the Usual Symptoms of a P0171 Code?

Symptoms of code P0171 include:

• Check Engine Light is on or flashing
• Loss of power
• Rough at idle
• Misfiring or “coughing” engine
• White spark plug tips

How Much Does It Cost to Fix Code P0171?

When you take your car to a mechanic for diagnosis, most will begin with an hour of labor diagnosing your specific issue. This normally costs between $80 and $150, depending on the shop’s labor rate. Then, if you have them do the repairs, many, if not most, businesses will apply this diagnosis cost to any required repairs. A shop will then be able to provide you with an accurate quotation for repairs to fix your P0171 issue.

Repair Estimates for P0171

One or more of the following repairs may be required to resolve the underlying issue for error number P0171. The estimated cost of each repair includes the cost of the relevant parts and the cost of labor required to complete the repair.

How Does Your Mechanic Diagnose the P0171 Code?

Assuming no other fault codes are present, a mechanic can diagnose the P0171 by using a vacuum gauge to examine the engine for suction leaks.

• A vacuum leak will produce a hissing sound that is normally only audible when the engine is shut off.
• A fuel pressure gauge is also used to inspect the fuel pressure sensor and the MAF sensor (mass airflow).
• The engine’s vacuum and fuel pressure must be within the manufacturer’s standards to maintain a correct air/fuel ratio. Therefore, these two checks will usually determine the source of this error code.
• If the reason is still unknown after the mechanic has done these two checks, the problem is most likely with a sensor.
• The mechanic would then use the manufacturer’s technique to test the mass airflow and oxygen sensors.
• If all of these tests are completed and no problems are detected, the issue is most likely with the powertrain control module.

Common Errors in P0171 Code Diagnosis

A common mistake is failing to look at any technical service bulletins for your specific car model that may be relevant to this issue.

Although not every issue code is associated with a technical service bulletin, it is always a good idea to double-check. They can save you a tremendous amount of time and work.

Will a P0171 Code Clear Itself?

The odds are that it will not. If you notice this code, you should get it checked out as soon as possible.

How do I fix code P0171?

You can usually fix P0171 using the following steps:

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

Can a dirty air filter cause a P0171 code?

If your car’s air filter becomes blocked or extremely unclean, it will hinder or restrict the flow of air. This, in turn, results in a lean running state. A dirty or defective MAF sensor, or a clogged fuel filter, can all be responsible for the P0171 code.