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2008 chevy trailblazer_ls
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Discussion Starter · #1 · (Edited)
I have a 08 trailblazer and it just started to throw a PO171 system too lean bank 1 code. What do I do to fix. The truck seems to be running great.
 

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2007 chevy trailblazer_ls
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https://www.obd-codes.com/p0171

A lot of times, cleaning the MAF sensor and finding/fixing vacuum leaks fix the problem. If you're on a tight budget, start there, but that may not be the fix for certain. So, possible solutions include:
•Clean the MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
•Inspect all vacuum and PCV hoses, replace/repair as required
•Inspect all hoses and connections in the air intake system
•Inspect and/or test the intake manifold gaskets for leakage
•Check for a dirty fuel filter and proper fuel pressure
•Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool
•If you have access, you may want to run a smoke test
I would suspect a dirty MAF sensor first.
 

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2006 gmc envoy_slt
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Viewing it as a good thing that I don't have to post here often considering my son's 2006 Envoy has 193k on it.

Ideally you'll want to monitor short and long term fuel trims using an advanced scan tool

I am getting P0171 and running the truck with scan tool connected STFT is in the low single digits (hopping between positive and negative) basically near zero. And the LTFT is in the mid-teens to mid-20s. And these were done at idle, 1500 and 2000 rpms. Would these numbers indicate Ole Ed the Envoy does not have a vacuum leak? Am I looking at the correct thing? What other numbers should I be reading to track this down and avoid throwing parts at it. Thanks in advance.
 

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2006 chevy trailblazer_lt
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Re: P0171 Trouble Code

I have a 08 trailblazer and it just started to throw a PO171 system too lean bank 1 code. What do I do to fix. The truck seems to be running great.
Yourself and I are not too far from each other; I live in Bensalem. I too have the same P0171 Trouble Code. I have been tracking down probable causes and replacing parts as necessary to resolve this common problem with the Trailblazer, Envoy and Bravada.

This common problem can be as a result of one issue or a combination of many issues, all at once. The best thing to do is to resolve the issues, one by one.

The simplest things to do is clean your air ductwork from the air filter to the throttle body, check and replace if necessary, the PCV hose and clean your Mass Air Flow Sensor. From there, check the breathing nipple on the front of the Air Intake Manifold. This YouTube Video shows the exact area to look for on the Air Intake Manifold. There should be a cap that goes on to here. If you don't have one on there, put a cap on there, preferably with one that is pliable rubber and not the cheap OEM cap for this port.

https://www.youtube.com/watch?v=VtI_tfFzYRc

If that process of cleaning the air ductwork & mass air flow sensor, replacing the PCV hose if necessary and adding/replacing the cap on the breathing port on the Air Intake Manifold does not resolve the issue, then replace the Secondary Air Injection Pump. This YouTube Video shows an in-depth diagnostics that leads to the Secondary Air Injection Valve replacement.

https://www.youtube.com/watch?v=k8LLDjmzngQ

On my truck, I have done all that I have included and I still have an intermittent P0171 Trouble Code. My truck needed all of the things I've listed to be corrected, so it is no biggie to be. But, the last two things that could cause the P0171 are the fuel pump and the Air Intake Manifold Gasket. Since you say your truck runs, as does mine, then the fuel pump is not the issue. This leads to the Air Intake Manifold Gasket being the last thing to replace.

You can attempt to tighten the Air Intake Manifold bolts, such as I have. This is why (including what I have replaced) have an intermittent trouble code P0171 and not a constant P0171 trouble code.

If you need further help, let me know. Yourself and I are local to each other and can help each other if need be. Good luck!


:tiphat
 

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FWIW - several of the intake manifold bolts were loose by several turns of the wrench. But what a PITA to get to them. I put a cushion down and laid across the top of the engine to get to the bolts.

Code has not reset since - but it had only set in cold weather anyway. So might not know for sure until next winter. Fairly confident snugging down the intake manifold bolts solved it for me.
 

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FWIW - several of the intake manifold bolts were loose by several turns of the wrench. But what a PITA to get to them. I put a cushion down and laid across the top of the engine to get to the bolts.

Code has not reset since - but it had only set in cold weather anyway. So might not know for sure until next winter. Fairly confident snugging down the intake manifold bolts solved it for me.
Yup, same here... I had strong code set in cool or cold weather, but intermittent code set in warm or hot weather. Thus, the intake manifold gasket is the culprit in this case. I'll either try tightening the intake manifold bolts again or just have my mechanic replace the gasket when I have the spare money.
 

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2008 chevy trailblazer_ls
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Discussion Starter · #8 ·
PO171 code

Yourself and I are not too far from each other; I live in Bensalem. I too have the same P0171 Trouble Code. I have been tracking down probable causes and replacing parts as necessary to resolve this common problem with the Trailblazer, Envoy and Bravada.

This common problem can be as a result of one issue or a combination of many issues, all at once. The best thing to do is to resolve the issues, one by one.

The simplest things to do is clean your air ductwork from the air filter to the throttle body, check and replace if necessary, the PCV hose and clean your Mass Air Flow Sensor. From there, check the breathing nipple on the front of the Air Intake Manifold. This YouTube Video shows the exact area to look for on the Air Intake Manifold. There should be a cap that goes on to here. If you don't have one on there, put a cap on there, preferably with one that is pliable rubber and not the cheap OEM cap for this port.


If that process of cleaning the air ductwork & mass air flow sensor, replacing the PCV hose if necessary and adding/replacing the cap on the breathing port on the Air Intake Manifold does not resolve the issue, then replace the Secondary Air Injection Pump. This YouTube Video shows an in-depth diagnostics that leads to the Secondary Air Injection Valve replacement.



On my truck, I have done all that I have included and I still have an intermittent P0171 Trouble Code. My truck needed all of the things I've listed to be corrected, so it is no biggie to be. But, the last two things that could cause the P0171 are the fuel pump and the Air Intake Manifold Gasket. Since you say your truck runs, as does mine, then the fuel pump is not the issue. This leads to the Air Intake Manifold Gasket being the last thing to replace.

You can attempt to tighten the Air Intake Manifold bolts, such as I have. This is why (including what I have replaced) have an intermittent trouble code P0171 and not a constant P0171 trouble code.

If you need further help, let me know. Yourself and I are local to each other and can help each other if need be. Good luck!



Hey Irishrockdoc, Thanks for the advice. I found that almost all of the intake manifold bolts were loose. I put in a new gasket and cleared the code and has been running great ever since
 

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Hi guys,

I have full resolve on my '06 Trailblazer with the P0171 Trouble Code. I had my mechanic smoke test my engine and as I suspected, the intake manifold gasket was the culprit all along. It is ok though, as I needed to repair all the other items I've previously stated in this thread, anyway.

I had my mechanic replace the spark plug well o-rings (I had oil inside of cylinder #3 spark plug well,) replace the valve cover gasket, install new spark plugs, install new intake manifold gasket and change oil & filter for emissions. A complete, full suspension package and new tires were installed for mechanical and then finally the state & emissions inspections were done.

With the P0171 Trouble Code, save yourself a headache and do all these repairs, in no particular order:

1. Clean the intake manifold and replace the intake manifold gasket.
2. If dry rotted, replace the PCV breather hose.
3. If applicable, replace missing or dry rotted vaccum cap from the passenger's side of the front of the intake manifold.
4. If applicable, replace the vacuum hose that runs from the passenger's side of the front of the intake manifold to the air intake box.
5. If applicable, replace the secondary A. I. R. injection valve and gasket.
6. Clean or replace the mass air flow sensor.
7. Remove and clean the entire throttle body. If the throttle body gasket is bad, replace it.
8. Clean the inside of the entire air intake tubing and air intake box.
 

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2002 chevy trailblazer_lt
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Re: P0171 Trouble Code



Yourself and I are not too far from each other; I live in Bensalem. I too have the same P0171 Trouble Code. I have been tracking down probable causes and replacing parts as necessary to resolve this common problem with the Trailblazer, Envoy and Bravada.

This common problem can be as a result of one issue or a combination of many issues, all at once. The best thing to do is to resolve the issues, one by one.

The simplest things to do is clean your air ductwork from the air filter to the throttle body, check and replace if necessary, the PCV hose and clean your Mass Air Flow Sensor. From there, check the breathing nipple on the front of the Air Intake Manifold. This YouTube Video shows the exact area to look for on the Air Intake Manifold. There should be a cap that goes on to here. If you don't have one on there, put a cap on there, preferably with one that is pliable rubber and not the cheap OEM cap for this port.


If that process of cleaning the air ductwork & mass air flow sensor, replacing the PCV hose if necessary and adding/replacing the cap on the breathing port on the Air Intake Manifold does not resolve the issue, then replace the Secondary Air Injection Pump. This YouTube Video shows an in-depth diagnostics that leads to the Secondary Air Injection Valve replacement.


On my truck, I have done all that I have included and I still have an intermittent P0171 Trouble Code. My truck needed all of the things I've listed to be corrected, so it is no biggie to be. But, the last two things that could cause the P0171 are the fuel pump and the Air Intake Manifold Gasket. Since you say your truck runs, as does mine, then the fuel pump is not the issue. This leads to the Air Intake Manifold Gasket being the last thing to replace.

You can attempt to tighten the Air Intake Manifold bolts, such as I have. This is why (including what I have replaced) have an intermittent trouble code P0171 and not a constant P0171 trouble code.

If you need further help, let me know. Yourself and I are local to each other and can help each other if need be. Good luck!


:tiphat
Is there a video on tightening the air manifold gasket?
 
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