How to Fix a P0171 Code – Cost, Causes, and Symptoms

Picture this -Your morning is going swimmingly, and you’re on your way to work on time. But then you try to start your car and discover that your Check Engine light is on and the engine is running rough. So, you pull out your trusty OBD II scan tool or code reader and discover that you have a P0171 code on your vehicle. Why did this happen, and what can you do to fix it?

What does the P0171 code mean?

A Code P0171 or system too lean bank 1 means either too much oxygen or too little fuel in the exhaust. This is a ‘lean’ condition or a ‘low fuel trim’ code.

The P0171 OBD-II code indicates that the fuel system on the first bank of the engine is weak or that a vacuum leak exists near this side of the engine. A lean state happens when the engine receives either too little or too much fuel.

What causes a P0171 code?

Some possible causes of a P0171 engine code are

• Vacuum leak
• Weak fuel pump
• Broken fuel pressure regulator
• Blocked fuel filter
• Faulty powertrain control module
• Defective injectors
• Faulty oxygen sensors
• Clogged catalytic converter
• Problems with the mass airflow sensor

Is it OK to drive with a P0171 code?

A lean fuel trim code, such as P0171, creates performance issues that might result in costly damage. These issues might range from low fuel economy to poor engine performance to internal engine damage. In addition, your car’s catalytic converter could be damaged if this code is stored for a long time. Catalytic converters are very expensive to replace. Therefore, it’s better to avoid driving with a P017.

What are the usual symptoms of a P0171 code?

Symptoms of code P0171 include:

• Check Engine Light 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.

• Vacuum leak fix: $100-$200
• MAF replacement: $300.
• Fuel pump: $1300-$1700
• Fuel pressure regulator: $200-$400
• Repairing an exhaust: $100 to $200 (if welded to repair)
• Oxygen sensor: $200-$300

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:

• Replace the fuel pump or fuel filter
• Change the fuel pressure regulator
• Replace the powertrain control module
• Change one or more injectors
• Replace one or more oxygen sensors
• Change the mass airflow sensor
• 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.

Can bad spark plugs cause P0171?

Quite unlikely. A vacuum leakage downstream from the MAF sensor or a defective MAF sensor is the most common cause of a P0171 (too lean, Bank 1) code.

Can a bad PCV valve cause P0171?

Yes, Vacuum or intake leaks, low fuel pressure, a defective PCV valve, or a faulty MAF sensor are the most typical reasons for the P0171 code. However, other factors can potentially contribute to the P0171 error code.

Can a bad O2 sensor cause P0171?

The actual issue may not be a broken O2 sensor but rather low fuel pressure, engine vacuum leak, or dirty fuel injectors that cause the engine to run lean.

Can a bad gas cap cause a P0171 code?

It does not set a false code. P0171 is a lean code caused by a vacuum leak, mass airflow failure, faulty PCV valve, or low fuel pressure.

What causes code P0171 in a Chevy?

A vacuum leak, which brings more air into the air-fuel mixture, or a poor fuel system, that does not inject enough fuel into the air-fuel mixture, can cause lean conditions in a Chevy. To keep the engine operating properly, the powertrain control module (PCM) attempts to compensate for the lean state by injecting more gasoline into the mixture in an attempt to maintain the proper 14.7:1 ratio. When these modifications become too large, the Chevrolet P0171 code is activated.

What causes P0171 in a Toyota?

A P0171 code typically indicates that your Toyota is experiencing issues with a dirty or defective mass airflow (MAF) sensor or a vacuum leak downstream of the MAF sensor (perhaps in the PCV line or the valve itself). Of course, this signal could also indicate a faulty O2 sensor in bank 1.

What causes P0171 in a Ford?

A dirty mass airflow (MAF) sensor is one of the most common causes of Ford P0171 and P0174 lean codes. Dirt can adhere to the MAF sensor wire and develop a coating, slowing the sensor’s reaction to variations in airflow. Fuel vapors that back up via the intake manifold and throttle body after the engine is turned off can also contaminate the MAF sensor. The vapors can cover the sensor wire with a waxy coating. As a result, the MAF sensor underreports airflow, leading the powertrain control module (PCM) to inject insufficient fuel to maintain a correctly balanced air/fuel ratio. As a result, your Ford’s engine runs lean and generates a P0171 or P0174 code.

---

Here’s more info on top-rated airport parking, the best parking spots in your city, the most affordable auto insurance for your car, and top-rated car washes near you.

---