Fuel lean code P0171?

Tiny
B-RAD2
  • MEMBER
  • 2020 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 48,500 MILES
I’ve been having intermediate problems with this code, it’s a capless gas tank and I’ve been opening the cover, and the code usually goes away but only for a few days.
Is there a bad seal in it and if so, which parts are needed to be replaced? I also noticed a hose that is disconnected to what I believe is called the snorkel, it’s connected to the throttle body and air filter housing. I appreciate any help.
Wednesday, February 28th, 2024 AT 4:14 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,748 POSTS
Hi,

The code is specific to a lean fuel mixture specific to bank 1. If there was an issue with the fuel tank capless system, it wouldn't be limited to only one side of the engine.

So, by chance have you noticed an exhaust leak on the one side of the engine near the exhaust manifold (pre-catalytic converter)? What do you do that causes the light to go off for a few days? You mentioned a cover. Which cover are you referring to? Does the vehicle seem to run properly? Have you ever noticed a misfire?

We could have a failing fuel injector, fuel pressure-related issue, exhaust leak, vacuum leak, and so on, so I'm trying to narrow things down.

Please keep in mind, if this is an emissions-related issue, and it sounds that way, it may be covered under the emissions systems new vehicle warranty for up to 8 years or 100K miles based on the cause and where you are located.

Let me know.

Joe
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Wednesday, February 28th, 2024 AT 8:16 PM
Tiny
B-RAD2
  • MEMBER
  • 11 POSTS
I haven’t noticed a misfire, and the cover for the gas tank that is spring loaded, I figured if I had air getting into my fuel system then that’d be the first spot to check. And what are some ways to find an exhaust leak? Is it more or less the same way to find a vacuum leak?
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Thursday, February 29th, 2024 AT 4:43 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,748 POSTS
Hi,

If there is an exhaust leak, usually it will be something you hear. It may even sound like a ticking. Often, people use something like carburetor cleaner to locate an engine vacuum leak. Don't spray that on the exhaust. It could cause a fire.

Here are two links you may find helpful:

https://www.2carpros.com/articles/step-by-step-guide-how-to-check-for-an-automotive-exhaust-leak

Here is a link that explains how to locate a vacuum leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know if it helps.

Next, by any chance do you have access to a live data scan tool? If you do, let me know what the short-term fuel trims are.

Let me know.

Joe
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Thursday, February 29th, 2024 AT 7:46 PM

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