VW/Audi P0171 Engine Fault Code – Diagnosis & Repair

by | Oct 12, 2022 | Audi, News, Volkswagen, VW | 0 comments

Failure Code P0171: Too Much Oxygen in the System in a Volkswagen or Audi (Bank 1)

For a P0171 error code, which indicates “System Too Lean” or “Fuel Trim System Lean Bank 1,” look for your CEL (Check Engine Light) to be on.

Just exactly does this imply, anyway? When the engine displays “System too lean Bank 1,” it indicates that the first bank is either not getting enough fuel or too much air. This obviously isn’t good for the engine, and it has to be fixed right now to prevent more harm.

When you observe this code the vast majority of the time, it is almost certainly due to a vacuum leak, which might be caused by a broken vacuum hose or a malfunctioning PCV Valve. Although this is often covered by the manufacturer’s warranty, you may incur diagnostic fees if you take the vehicle to a dealer.

See below for diagnostic advice, replacement components, and how-to videos if you’re attempting to repair it yourself.

Do I need to have it fixed before I go back behind the wheel of my Volkswagen or Audi with the P0171 fault code?

When many error messages appear, this is a frequent concern. Your engine’s performance will suffer regardless of how severe the vacuum leak is. As the leak becomes worse, the engine’s performance will deteriorate, making it less desirable to continue driving with this code. If you really need a brief response, the answer is “yes,” although the advice against doing so is strong.

In this post, we will be offering components and do-it-yourself tutorials to ease this difficulty on a 2.0t TSI.

VW/Audi P0171 Symptoms

  • The Check Engine Light (CEL) has come on
  • It sounds like the engine is stuttering
  • Decreased efficiency of the engine
  • Problems starting the engine
  • The car keeps turning off and won’t start

P0171 Volkswagen and Audi Engine Error: Possible Causes

  • A leak has been discovered in the vacuum hose
  • PCV Valve (Positive Crankcase Ventilation) not working
  • The High-Pressure Fuel Pump has failed
  • Problems with the ignition (Fault Codes:  P0301, P0302, P0304,P0300, P0303)
  • Loss of Intake Air Pressure (Fault Code: P0174)
  • Broken Oxygen Detector
  • Malfunctioning Mass Air Flow (MAF) Sensor.

Fixing an Automobile with an Error Code P0171 in the Engine

It’s not too difficult to diagnose, therefore we recommend doing it yourself if the car isn’t under warranty. Ideally, you would investigate each part of the engine in order, beginning with the most obvious potential culprits. Each possible explanation for a P0171 code is presented in descending order of plausibility. If you’re trying to figure out what this error number means, the video down below is a fantastic reference.

Methods for Detecting a Leaking Vacuum Hose

If your Volkswagen or Audi is showing the P0171 engine code, the likelihood is high that a leaking vacuum hose or a malfunctioning PCV valve is to blame. Identifying the source of a vacuum hose leak may be challenging, but the primary hose of concern is the one that connects the suction pipe to the vacuum pump. This is the hose that should get the most of your attention.

Fixing a Leaky PCV Valve

Another common cause of this code is a faulty PCV valve, as mentioned above. In a nutshell, a PCV valve collects unburned gasoline and oil vapors, therefore lowering emissions. Take it to a repair shop, and you’ll be looking at an approximate cost of $400 to replace it.

Maintenance of a High-Pressure, Low-Temperature Gas-Purge (High-Pressure Fuel Pump)

As you go up to older automobiles, you may begin to understand why these things are thus. An HPFP is exactly what it sounds like; it converts ordinary gasoline into the high-pressure fuel required for direct injection. Because of the high price of the necessary replacement parts, having this fixed in a shop would set you back about $800.

Ignition Coil Replacement Instructions

Having a P0171 code accompanied by engine malfunction codes ( P0304, P0301, P0302,P0300, P0303) is not uncommon, however it is vital to repair or analyze the 3 others above before presuming a defective coil is to blame for this code. Voltage from the battery is converted by the ignition coil into the spark plugs’ firing voltage. Once it is discovered that a malfunctioning ignition coil or coil pack is to blame for a misfire, it is recommended that the whole unit be replaced.

Locating a Leak in the Intake Manifold

Intake manifold failure may occur due to either coolant leakage or air leakage from external passages, both of which can result in lean conditions. Intake manifolds are used to filter incoming air and distribute it to the engine’s cylinders in a controlled manner.

Repairing a Malfunctioning Oxygen Meter

Finally, if none of the above solutions work, a defective O2 sensor may be to blame for the error message. The exhaust gas oxygen content is determined using an O2 sensor.

Conclusion For The P0171 Engine Fault Code

In conclusion, a vacuum leak is probably the cause of the P0171 code your car is showing you. It’s possible to drive it for a little while, but you shouldn’t. This article was originally intended for a VW/Audi 2.0t engine; however, if you’re having this issue with a different engine or car and would like some assistance, please inform us what you’re struggling with in the comments and we’ll do our best to help! We wish you and your car the best of luck and hope that this information has been useful to you.

Further Reading: https://www.way.com/blog/how-to-fix-a-p0171-code/#:~:text=A%20Code%20P0171%20or%20system,this%20side%20of%20the%20engine.

Dmitry Petrov

Dmitry Petrov is an engineer who specializes in materials science, and has a deep passion for all things related to automotive technology. He is a true motorhead at heart, and spends much of his free time tinkering with engines and studying vehicular dynamics.


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