P0174 Code: What Are The Causes, Symptoms & Fixes?

The most fuel-efficient combustion engines have 14.7 parts air to 1 part fuel in the mixture. When there are more than 14.7 parts air to 1 part fuel in the air-fuel mixture, a lean condition occurs, and the P0174 code is activated.

A lean state can be caused by a vacuum leak, which adds extra air to the air-fuel combination, or by a faulty fuel system, which injects insufficient fuel into the mixture. In order to maintain the correct 14.7:1 ratio, the powertrain control module (PCM) attempts to correct the lean condition by adding extra fuel to the mixture. When these changes get too big, code P0174 appears.

So, what does code P0174 mean? What is the cause? What are the costs and methods of fixing it? In this blog, we will cover all this information in detail. So, let’s get started!

What is the meaning of code P0174?

Source: carcarehacks

The P0174 engine code is a Diagnostic Trouble Code (DTC), and it displays the message “System Too Lean (Bank 2)”. It denotes an excessively lean air-fuel ratio in your car. The gas in your car needs to mix with air before it can burn and power your car. When the gas and air are present in the right amounts, the mixture burns fully. A mixture that is too lean will not allow your car to operate at its best.

P0171 and P0174 are the error codes that appear in conditions of leanness. A lean condition in cylinder bank 1 sets off the P0171 code, while a lean condition in cylinder bank 2 sets off the P0174 code. A lean condition can be partially restored by the Engine/Powertrain Control Module (ECM/PCM), but not completely. Therefore, the P0174 code is stored by the ECM/PCM to alert the user to this problem.

What are the Causes of the P0174 code?

Source: auto-repair-tools

If your engine displays the P0174 error code, it means that the air-to-fuel ratio is incorrect. Unfortunately, there are a number of causes for this, including defective sensors, fuel injector problems, and air leaks. For a professional diagnostic, it is recommended to take it to a mechanic. Most of the time, the P0174 code is caused by the things listed below.

  • Mass airflow (MAF) sensor issue.
  • Obstruction in the fuel injectors and fuel filter.
  • Fuel pump weakness is increasing.
  • Decreasing the regulator’s fuel pressure.
  • There could be damage or cracks in the PCV line or vacuum connector.
  • A damaged oxygen sensor.
  • PCM-related problems.
  • Leak in the booster brake system.

Symptoms of P0174 Code

Source: carparts

The following symptoms of the P0174 error code could show up on your car:

  • Check the engine light is on.
  • A reduction in engine power. As you accelerate, you’ll feel as though you have less power.
  • A misfire occurs in the engine.
  • An increase in the fuel used.
  • Idling roughly.
  • The engine stalls.

Nitrogen oxide (NOx) is a pollutant released by lean automobiles that can aggravate conditions like asthma in sensitive individuals. Running lean conditions can also lead to a misfire, which, over time, can damage your car’s internal components and ruin the catalytic converter when it uses raw fuel. If you spot any of the above signs, you should take your car to a professional mechanic as soon as possible.

Diagnosing the P0174 Code

Source: autozone

The best course of action is to get your car checked out by a professional mechanic as soon as the engine code P0174 appears. The following actions will be taken by the mechanic in order to diagnose the problem with your vehicle precisely.

  • Perform a test on the fuel pressure.
  • Check for leaks in the vacuum lines and intake system.
  • Look for leaks in the valve cover or worn-out hoses.
  • Investigate the PCV valve.
  • Use a multimeter or a scan tool to inspect the mass airflow sensor.
  • With the use of a multimeter or scan tool, check the relevant oxygen sensor.

Common Misdiagnosis

  • Making changes to a part without first trying it to see if it is broken.
  • Not checking the intake system for leaks or rips.

Fixing the P0174 Code

Source: ndtv

Once the diagnosis has been made, the next step is to apply the necessary changes to remove this engine code. These are a few actions that can resolve the problem.

  • Replace or clean the mass airflow.
  • Changing an oxygen sensor that is broken.
  • Vacuum line replacement.
  • Replacement of PCV valve.
  • EGR valve replacement.
  • If there is a leak in the brake booster, replace it.
  • Changing the gasket on the valve cover.

Fixing the P0174 Code by Yourself

Source: permeke.be

The P0174 engine code is something you can fix on your own. However, it can be difficult to identify the source of your air-fuel combination issue. Look at the wire harness and connectors first. Make sure to thoroughly inspect for any pushed-out, damaged, bent, or rusted items, particularly connecting pins.

If nothing seems wrong or you’re not sure how to fix the problem, take your car to a mechanic for a thorough diagnostic examination. After that, you can decide if you can manage the problem on your own. If so, you might need to do the following actions.

  • Replace the damaged sensor.
  • Change the spark plugs.
  • Do a fuel injector cleaning.
  • Replace or reconnect the PCV hose.

Cost of fixing P0174 Code

Source: motorverso

Repair costs vary depending on what caused the P0174 engine code and whether you can do it yourself or if you need to hire a professional. Snapping the Positive Crankcase Ventilation (PCV) valve back into position could be the only remedy if it is attached incorrectly. A vacuum leak repair done by a professional might go up to $1000.

Below are a few possible causes of a P0174 engine code, along with an estimate of the cost to get it serviced by a professional. Pricing will vary depending on factors like location and vehicle selected.

ItemEstimated cost
Vacuum leaks$1000
Fuel pump$1300-1700
Fuel pressure regulator$200-400
Repairing exhaust$100-200
Oxygen sensor or air-fuel sensor$200-300
Cleaning MAF$100
Replacing MAF$300
Replacing PCV valve$75-100
Replacing spark plug$150
Exhaust gas leak$300-400
Defective O2 sensor$325-400

Can you drive with a P0174 code?

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The P0174 code does not instantly cause damage to your car’s components when you drive it. However, if you keep your engine running lean, it could overheat and perhaps break internal engine components. Running rich is always better than lean since the extra fuel will help to keep the engine cool.

Since other car issues could go unnoticed for a while, you might be inclined to overlook a P0174 code for a while. On the other side, since your engine isn’t getting enough gasoline, an issue with the air-fuel mixture can result in serious drivability issues.

If you encounter this error code, do not make full acceleration pulls. Rather, take a slow journey to the workshop and identify the problem beforehand. Also, some of the things that are causing this problem may have side effects that could be dangerous. For instance, you could be exposed to deadly carbon monoxide pollutants via an exhaust leak.

Frequently Asked Questions

Can an exhaust leak lead to the P0174 code?

The most likely cause of a check engine light on and stored P0171 and P0174 codes is a vacuum leak. These codes are set by the car’s computer when it finds excessive oxygen in the exhaust.

Can a bad fuel filter result in the P0174 code?

Yes. If the fuel pump or gasoline filter in your car is damaged, the code will activate.

Can bad spark plugs lead to the P0174 code?

Yes. If the code appears, there could be a problem with your ignition, such as worn-out spark plugs or vacuum leaks.

Can a fuel pump cause a P0174 code to appear?

The code may activate due to a defective fuel pump or a clogged fuel filter. If the oxygen sensor sends a reliable indication that the fuel mixture is too lean, the PCM will keep adding gas to the engine’s combustion chambers.


The P0174 code indicates that Bank 2 has less gasoline but too much air. If you continue to drive the vehicle in this state, you could end up damaging the engine. When the code appears, take your automobile to a professional and get it fixed right away.

When trying to figure out what caused the P0174 error, it’s essential to check every possible cause. This DTC can appear as a result of a defective MAF sensor, clogged fuel injectors, vacuum leaks, and other problems. So, it is necessary to figure out the cause precisely and repair it timely.

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