The P0174 OBD-II error code is not manufacturer-specific, but rather a generic code that applies to various makes and models.
If your vehicle is triggering a P0174 code, read our guide below to learn more about the issue and find out how you can diagnose and/or fix it.
What Does Code P0174 Mean?
Diagnostic trouble code (DTC) P0174 stands for “System Too Lean (Bank 2).” It indicates that your car’s computer has detected a lean running condition.
A lean condition is brought about by an imbalance in the air to fuel ratio due to either insufficient fuel (from, say, a weak fuel system) or excessive air entering the engine. The bank 2 portion indicates that the problem is concentrated on the side of the engine opposite the #1 cylinder.
The error codes for these conditions are P0171 and P0174. The former is triggered when a lean condition occurs in cylinder bank 1, while P0174 appears when it occurs in cylinder bank 2. Note that it’s possible to register trouble codes P0171 and P0174 in certain circumstances.
Even though the powertrain control module (PCM) is built to be able to bring a lean bank 2 condition back to normal, it can only do so up to a certain extent, thus the P0174 code may be needed to alert the user to resolve this issue.
To better understand what a lean condition is, let’s delve into how a combustion engine works. Ideally, the ai to fuel ratio burned by the engine is 14.7 parts air to 1 part fuel. When the ratio of air is lower and the fuel is higher than the standard, it results in something referred to as a “rich” mixture. If there is not enough fuel, but the air exceeds the standard, it results in a “lean” mixture.
In order to alleviate the imbalance in the air to fuel ratio, the PCM works in conjunction with the oxygen sensors or O2 sensors to gauge the amount of oxygen in the exhaust. It then regulates the air to fuel mixture by adding or reducing the amount of fuel as needed.
When a fault code P0174 is detected in your ride, it means that the PCM can no longer perform the necessary air to fuel adjustments. This could lead to poor engine performance and increased emissions.
Many owners have reported P0174 for the following makes: Ford (especially on a Ford F-150), Chevrolet, BMW, Toyota, Nissan.
What Causes the P0174 Code?
Here’s a list of the most common reasons why the P0174 code could register in your ride:
- Vacuum leak
- Malfunctioning mass airflow (MAF) sensor
- Clogged fuel filter
- Failing fuel pump
- Clogged fuel injectors
- Failing fuel pressure regulator
- PCM issues (e.g., software in need of an update)
- Worn-out oxygen sensor
What are the Common Symptoms of the P0174 Code?
You may find your vehicle displaying the following symptoms for error code P0174:
- Illuminated check engine light
- Loss of power
- Engine misfires
- Surge on acceleration
- Rough idling
- Difficulty when starting the car
- Engine stalling
Some of these symptoms are more noticeable at lower speeds and RPMs. If you find your ride exhibiting any of the symptoms above, have it diagnosed immediately by a professional. You may also conduct the diagnostic procedures yourself.
How to Diagnose the P0174 Code
P0174 must not be ignored. All potential causes must be looked into to come up with the correct diagnosis. If you don’t have enough DIY auto repair experience, it may be best to take your vehicle to a mechanic. However, if you still want to take a stab at the diagnosis process, the video below can help you do it correctly.
How Do Mechanics Diagnose Code P0174?
Because code P0174 has so many potential causes, professional mechanics will typically consult a repair database before performing any diagnostics.
After that, they will usually use advanced equipment to troubleshoot the problem. For example, they may use a scan tool to view live data or a smoke machine to pinpoint vacuum leaks. They may also check fuel pressure with a gauge or test individual sensors with a multimeter or oscilloscope.
How to Fix the P0174 Code
There are a variety of reasons why code P0174 could register on your ride, so there’s no single solution to resolve the problem. For example, you may have to replace the fuel pump if it’s part of the problem.
The first thing you need to do is identify the root cause of the problem accurately, and look for parts that are contributing to the issue before doing any repairs. In many cases, replacing faulty parts is your best option.
Make sure you only replace a part once you’re completely sure that it’s faulty after thorough testing. Some people immediately replace their oxygen sensor or positive crankcase ventilation (PCV) valve upon getting poor readings when the problem was actually a vacuum leak or dirty MAF sensor.
Always remember that all vehicles are different. Consult the factory repair information for your application to safely and properly fix the error code.
Consider getting a service repair manual, such as Chilton or an ALLDATA subscription, to access the factory repair information and service instructions you need. Search for confirmed fixes for your vehicle. You may also talk to your mechanic for expert advice.
Estimated Repair Cost
The cost of resolving this fault code varies depending on what triggered the issue. Some problems can be addressed with a repair service, a part replacement, or a combination of both.
Below are some of the parts that you may need to replace if your system logged a fuel system too lean issue in the cylinder bank 2 and their price ranges. Note that these figures do not include labor costs.
- MAF sensor – $6 to $580
- Oxygen sensor – $3 to $480
- Fuel filter – $6 to $303
- Fuel pump – $10 to $2,100
- Fuel injector – $11 to $780
- Fuel pressure regulator – $10 to $360
Other Notes About P0174
Don’t ignore a P0174 code—address it as soon as possible. A poorly running engine due to a lean fuel mixture can fail if left untreated. A small, inexpensive problem could worsen and make your ride undrivable.
Instead of shrugging it off, remember that a P0174 is a serious issue that demands your attention. The consequences of ignoring this trouble code include reduced fuel economy, weak performance, poor ride quality—and even engine damage. Keep these in mind when dealing with other fault codes as well.
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