P0174 Fault Code

Long Description

Fault code P0174 means that the engine control module (ECM) has detected that the second bank of the engine is running too lean.

Running lean is a term used to describe when there is too much air or too little fuel at any given time in the engine. Engines run on an ideal air-fuel mixture of 14.7 parts of air to 1 part of fuel for petrol engines.

If the powertrain control module (PCM) cannot correct this by increasing the amount of fuel within a certain limit, this will trigger the fault code. This can also result in a P0170 code.

Bank 2 refers to the side of the engine that is opposite to the location of cylinder 1. This is only true for V-shape engines. This also means that only V-shape engines can suffer this fault code.

Only V-shape engines can suffer this fault code. This means BMW, Ford, and Lexus are some of the most commonly reported.

Other Signs of This Problem

As with most problems directly involving the combustion process of an engine, code P0174 comes with a host of fairly typical issues that can easily be recognized.

The most obvious of these is that the Check Engine light will illuminate.

Other signs should be fairly obvious as well. These include a loss of power, a rough idle, difficulty starting the vehicle, and even misfiring when driving. Acceleration should also be difficult.

If these symptoms are present even without fault code P0174, look out for the mirror code in bank 1. This is P0171.

What Could Be The Problem?

Because this fault code represents an issue with the air-fuel ratio, it can mean there is an issue in either system.

There are several sensors that specifically check for this type of issue. Any faults or damage to these sensors can easily result in this error or P0174 being displayed on an OBD2 reader. The mass airflow (MAF), oxygen, and air-fuel ratio sensors should all be checked.

Another issue is that there is unwanted air entering the vacuum which disrupts the ideal ratio. There can be leaks found in multiple places throughout the engine, particularly the positive crankcase ventilation (PCV) system.

If air is not the issue, then it is likely something in the fuel system. Low fuel pressure can come as a result of a faulty fuel pump and can provide too little fuel. Clogged or faulty injectors and filters can also cause this issue.

Fixes

Possibly the easiest step to take to fix this issue is to check for and repair vacuum leaks.

Another fix is to replace any damaged or faulty sensors. Again, these will be the MAF, oxygen, or air-fuel ratio sensors.

Replacing any faulty components in the fuel line is also a solution. This can result in needing one or more new fuel injectors, a fuel pump, or a fuel pressure regulator.

Seriousness

Fault code P0174 should be considered moderate to severe in terms of seriousness. While there is no risk of immediate damage to the engine, it can degrade it over a short amount of time if ignored.

It is strongly recommended to have this issue be resolved immediately.