While the P0174 OBD-II trouble code is not manufacturer-specific and is considered a generic powertrain code, it can be more common in certain car makes than others. More specifically, a P0174 is most often reported on Chevy and Ford vehicles.
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).” The code indicates that your car’s computer has detected a lean running condition.
A lean condition is brought about by an imbalance in the air-fuel ratio due to either insufficient fuel or excessive air entering the engine. The bank 2 portion of the code indicates that the problem is concentrated on the side of the engine opposite the #1 cylinder.
The error codes for lean 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.
Even though the Engine Control Module (ECM) is built to be able to bring a lean 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 air-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-fuel ratio, the ECM works in conjunction with the oxygen sensors to gauge the amount of oxygen in the exhaust. It then regulates the air/fuel mixture by adding or reducing the fuel as needed. When a fault code P0174 is detected in your vehicle, it means that the ECM can no longer perform the necessary air/fuel adjustment.
What Causes the P0174 Code?
The most common causes of the P0174 code are the following:
- Vacuum leak due to damaged intake manifold gaskets or punctured vacuum and positive crankcase ventilation (PCV) hoses
- 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 trouble code P0174:
- Illuminated Check Engine Light
- Loss of power
- Rough idling
- Difficulty when starting the car
- Engine stalling
Vehicles that run lean emit nitrogen oxide (NOx), which can be hazardous to one’s health and can cause respiratory ailments such as asthma. Running lean conditions can also cause a misfire, which can damage the catalytic converter with raw fuel and ruin the internal components of your vehicle in the long run.
If you find your ride exhibiting any of the symptoms above, have it diagnosed immediately by a professional.
How to Diagnose the P0174 Code
There are numerous potential causes for OBD-II code P0174. As such, diagnosis can be difficult.
For an idea of how to troubleshoot the code, check out the video below:
How to Fix the P0174 Code
There are a variety of reasons why code P0174 could register on your vehicle. There’s not a single solution to make the code disappear. 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 diagnose the code 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.
Always remember that all vehicles are different. Consult the factory repair information for your application to safely and properly fix the trouble code. Consider getting a repair manual, such as Chilton or an ALLDATA subscription to get the factory repair information you need.
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 vehicle undrivable.
Instead of shrugging it off, remember that an OBD-II code P0174 is a serious issue that needs your attention. The consequences of ignoring this trouble code include reduced fuel economy, weak performance, poor ride quality—and even engine damage.