How to Fix P0174 Code: What’s Behind this Fault and its Fixes

OBD2 Scanners is reader-supported. When you buy through links on our site, we may earn an affiliate commission.

Are you having trouble with your car and seeing the Check Engine Light illuminate? Are you seeing the P0174 code pop up on your OBD scanner and don’t know what it means? Don’t worry!

This blog post is for you. We’ll go over the causes, symptoms, diagnosis, and possible fixes of the P0174 error code. Hopefully, you can fix your vehicle and get back on the road in no time. Let’s get started!

What is Code P0174?

The P0174 is a diagnostic trouble code (DTC) for "System Too Lean Bank ." It is triggered when the PCM (Powertrain Control Module) detects too much air and insufficient fuel in the engine.

The Engine Control Module (ECM) is designed to maintain a certain air to fuel mixture ratio. It constantly adjusts the amount of fuel injected into the engine. The oxygen sensors monitor the air to fuel mixture. When the ECM sees too much air and not enough fuel, it will set code P0174.

Symptoms of Code P0174

Are you experiencing some symptoms but aren’t sure if it's due to this error code? To help you find out if your car is experiencing symptoms related to code P0174, here are some of the most common ones:

  • Check Engine Light is on
  • Decreased acceleration
  • Engine stalling
  • Rough idle
  • Increased fuel consumption
  • The engine may run lean.

Causes of Code P0174

When diagnosing the P0174 code, it is essential to know all the causes as it will help you fix the problem more effectively. So, if you plan to skip this part, we suggest you think again. Here are some of the most common causes:

  • A vacuum leak
  • Fuel injectors leaking
  • An intake manifold gasket that has failed
  • A faulty mass airflow sensor
  • Defective fuel pressure
  • A clogged air filter or a dirty throttle body

How to Diagnose Error Code P0174?

To properly diagnose the P0174 code, you need to check all the possible causes one by one. In that way, you can be sure that no stone is left unturned and your car will be running in no time. Did you recheck them? That's great! Let's now proceed to diagnose!

Check for Other Codes

As you would notice, checking for other codes is always included in our guide. That's because other codes can give you a hint on where to look for the main problem. To perform it:

  1. Get your OBD scanner and plugin into the car diagnostic port.
  2. Start the car and wait until the scanner reads all the data.
  3. Look for other codes that may be related to P0174.
  4. If you find any, write them down and look for their fixes as well because in some cases, fixing one code          will automatically fix the other.

Perform Visual Inspection

You may also notice that visual inspection is always included in diagnosing steps whenever we encounter a new problem. That's because the solution to any problem might just be staring us in the face most of the time. So, for P0174, what you need to look for are:

Vacuum leaks

One of the most common reasons why P0174 shows up is because of vacuum leaks. To check for this, use a can of carburetor cleaner and spray it around all the vacuum hoses, gaskets, and intake manifold. If the engine speed changes, then you leak.

Damaged or Malfunctioning Components

You need to check the air/fuel mixture components like the fuel injectors, oxygen sensors, and mass airflow sensor. If any of these are damaged or not functioning correctly, it will trigger a P0174 code. So fix it if necessary!

Wrong Fuel Ratio

Finally, the last thing you need to check is the fuel ratio. This is because a lean mixture can also cause this code to be triggered. To check this:

You will need a fuel pressure gauge. If the reading is below what is specified in the service manual, then there is not enough fuel being delivered to the engine, causing the lean mixture.

How to Fix Code p0174?

Now let's get to the fixing part. If you are uncomfortable doing this alone, we urge you to seek help from a professional mechanic. But, if you are keen on doing this yourself, we will guide you through it!

First, let’s check the most common cause of P0174, a faulty oxygen sensor. As mentioned earlier, this part is responsible for maintaining the correct air to fuel mixture ratio. When it gets damaged or worn out, it can no longer do its job properly, resulting in a lean mixture.

Now that we know the root cause, it's time to get our hands dirty and work! But before you start, make sure to have all the necessary tools and parts ready. Once you're all set, follow these steps:

  1. Locate the oxygen sensor. You'll usually find it mounted on the exhaust manifold or close to the catalytic        converter.
  2. Disconnect the sensor's electrical connector.
  3. Remove the oxygen sensor using a wrench or socket.
  4. Install the new oxygen sensor and tighten it properly.
  5. Reconnect the electrical connector.
  6. Start your engine and let it idle for a few minutes. 
  7. Check the engine light to see if it's still on; check if the P0174 returns.

Suppose you found out that the root cause is the faulty mass airflow (MAF) sensor, then you must clean it or replace it if necessary. Do you know how to replace a MAF sensor? Don’t worry, if you have a little knowledge about it, we will make it easier. Just follow the steps below, and you'll be done in no time.

  1. First, locate the MAF sensor. It's usually located near the air filter box or the engine's throttle body.
  2. Once you find it, disconnect its electrical connector.
  3. Using a screwdriver, remove the screws that hold the MAF sensor in place.
  4. Carefully pull out the MAF sensor and then clean it using a Mass Air Flow (MAF) cleaner.
  5. If the sensor is already damaged, you need to replace it with a new one.
  6. To do that, follow the steps above in reverse order. But of course, we will not leave you alone in the                process. So let's continue!
  7. Get your new MAF sensor and then connect its electrical connector.
  8. Secure the new MAF sensor in place using the screws you removed earlier.
  9. Start the engine and check if the code is gone.

Common Mistakes When Diagnosing the Code P0174

If you would notice, we always want you to check for all the possible causes of the issue. That is because we don't want you to make mistakes when diagnosing. However, it is often unavoidable, especially when new to this. So for you to avoid making the same mistakes, here are some of the most common mistakes:

  • Failing to Check for Leaks in the Intake System
  • Ignoring the Possibility of a Faulty Mass Airflow Sensor
  • Failing to Check for Vacuum Leaks
  • Assuming that the problem is with the O₂ sensors or the MAF sensor without inspecting the intake system
  • Replacing any components without verifying ists the roots cause.

Code P0174 FAQs

1. Is the P0174 code serious?

The level of risk of this error code is moderate. However, if you continue to drive with this error code, it can cause your engine to overheat and damage the engine.

2. Is it safe to drive with the trouble code?

Although you can drive having this code, it is not recommended because, as mentioned above, your engine could overheat, which is a risk to your engine and yourself if the temperature gauge is not working.

3. What can I do to prevent the P0174 code from returning?

The best way to prevent this code from coming back is to fix the issue accordingly and appropriately. Also, be sure to keep up with regular maintenance on your vehicles.

4. What would happen if I did not address the issue immediately?

If you did not address the issue immediately, your engine could overheat and cause damage to itself. So, if you don't want that to happen, make sure to have it checked by a mechanic or fix it yourself.

5. How much does it cost to fix the P0174 code?

The repair cost may vary depending on the severity of the issue. For instance, if the problem is just a vacuum hose, the cost can be around $50, and a clogged fuel filter for $100. But if you need to replace the mass airflow, it can be around $400 to $500.


The code P0174 is not as severe as we believe, so don't panic! However, it is recommended to address it as soon as possible as it could cause your engine to overheat. With the help of our guide, you may surely get your vehicle back in shape in no time!

So, are you ready to fix your car, or have you already fixed it? How did it go? Let us know your experience in the comments section below! We will be happy to know your thoughts! Thanks for reading!