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Figuring out why your Check Engine Light is on means deciphering OBD-II (or “OBD2”) codes, and that can be kind of annoying. That’s why Car Bibles did it for you! You’re welcome, now let’s get into solving your issue.

OBD2 P0174: What It Means

To make your vehicle, um, go, the engine needs fuel, air, and spark, to create combustion. When driving, your vehicle is constantly making adjustments to the air and fuel ratios. If the ECM, or “computer” can’t maintain the correct ratios, a check engine light is triggered. P0174 code, System Too Lean (Bank 2), means that there is too much air in the air to fuel ratio. “Bank 2” refers to the second bank of cylinders in “V” engines, usually including even-numbered cylinders.

Likely Symptoms

Here’s what you may experience due to the P0174 code.

  • Lack of power, air-to-fuel ratio mixture has too much air, and the engine can’t generate as much power.
  • Hesitation on acceleration or rough idle. The ECM can’t maintain a good air and fuel ratio to maintain idle.
  • Poor fuel economy. 
  • Sometimes, there may be no driveability issues

Probable Causes

  • Vacuum leak. Vacuum leaks could come in several forms, as several systems depend on vacuum or closed systems. Commonly, the intake manifold is a source for a vacuum leak. 
  • MAF sensor, or Mass Air Flow sensor calculates the total volume of air that is being used by your vehicle’s engine, and it is critical for correct air and fuel ratios. A broken or dirty MAF sensor could cause a lean condition.
  • Faulty ECM. The computer may be incorrectly interpreting information given from the vehicle’s sensors.

What Part Is Potentially Affected?

Aside from the reduced performance that comes with a lean-running engine, lean running conditions can cause serious engine damage.

Vehicles that run lean, run hotter combustion chamber temperatures. Those higher temperatures can burn holes in your engine’s valves, commonly called “burning a valve.” It can also create premature detonation (pinging or knocking), where the combustion happens before the cylinder has reached the top of its stroke.

Pinging can severely damage the pistons, and destroy an engine.

Possible Fixes

Here are the most common fixes to remedy the P0420 code.

  • Diagnose and repair vacuum leak. This may be a bit tricky since modern vehicles use vacuum for multiple systems. Yet, tracking down where the air is escaping (or being introduced, unnecessarily) in your vehicle’s vacuum system could be the ticket.
  • Clean (or replace) MAF sensor. A correctly functioning MAF sensor is critical to a correct fuel to air mixture. If you try to clean one, make sure you use a product specifically made for MAFs, not just regular carb cleaner or throttle body cleaner! MAFs are extremely sensitive and can be easily damaged.
  • Replace, repair, or reflash ECM. A faulty computer, either hardware or software could be the culprit. Generally, it may be more expensive to replace, though.

Finding The Parts You Need

Now that you’ve figured out what’s wrong with your hooptie, let’s talk about where you’re gonna find that part’s replacement.

There are plenty of places you can buy auto parts from, but Car Bibles gets paid if you click this Advance Auto link so that’s the one we’re serving up. Advance Auto Parts also has delivery, curbside pickup, and a host of helpful diagrams to aid your repair!

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