08 gasser canyon p0171 code

Chevy1925

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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funny, i figured id start a thread on DD about my wifes truck and started looking for an appropriate section to post in and found a new section was created for the new coli's lol.

regardless, its not exactly fitting here either so Nick, Rob, The McRats, Mike, ECT, please move if need be :hug:

So the other day my wife comes home saying her check engine light is one. Truck is an 08 GMC Canyon 3.7 I5 with 60k on it and 100% stock. Code is P0171 Lean bank. So i start diag on it.

o2 sensor tests out good. cycles between 100-900mV when in closed loop and will go full rich (980mV) when sprayed with carb cleaner into the throttle body.
pulled the intake off and made sure the common PCV hoses were hooked up and no cracking apart to the intake, good there
sprayed the intake manifold, intake, and vac hoses down with crab cleaner lookin for a change in fuel trims or o2 sensor as well as listening for a change in engine rpm.... nothing.
checked fuel pressure, steady at 58psi running.
I cleaned the MAF yesterday, didnt see anything out of the ordinary on it. Cleared the code as well so we will see if it comes back today on her way home.

Im pretty much out of ideas. maybe a stuck PCV valve? anyone have ideas? i think it needs a turbo personally :D
 
chevyburnout1

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
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Do you have the ability to watch the fuel trim numbers? Injectors and MAP sensor connectors were a decent issue on the 5 bangers. I had two that were just setting the P0171 code. Checked everything. Finally installed injectors and the fuel trims were perfect.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,667
5,813
113
Phoenix Az
looks like i can with efi live. they show percentage and were at 10% when first start up at operating temp, then fall to 0 to -2ish all at idle in nuetral
 
chevyburnout1

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
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Berthoud, CO
Hmm probably not injectors. Monitor the fuel trims while driving and under a load. I believe anything above 12% long term will set the code after a certain amount of time.
 
chevyburnout1

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
2,368
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38
Berthoud, CO
Skewed MAF sensor could cause a lean symptom under load. All I can think of right now that you haven't already checked. Let me know!
 
chevyburnout1

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
2,368
1
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Berthoud, CO
The more I think about it the MAP sensor and injector issues were on the earlier engines anyhow.

I've been told a good rule of thumb for MAF readings at idle should roughly equal the engine displacement in liters. So I want to say roughly 3.7g/s. I do get my nomeclature mixed up sometimes, but I believe it's the g/s. But with your fuel trims readings warmed up at idle are around 0% you probably wont see anything wrong. Best bet is to monitor fuel trims warm and cold under different loads and see if they skew positive under a certain condition.
 
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