P0171 & Check Engine Light, No Misses or issues

[donjetman]

2007 Yukon Denali 6.2L L92 w/192k miles.
Past couple of weeks I keep getting the check engine light and code P0171-Fuel System Lean Bank 1.
No Mis-fires. Vehicle runs great, getting good mpg as usual, no other issues.
so
I ran a can of SeaFoam, no change.

18 mths and 18k miles ago installed 4 new amazon GM Genuine Parts O2 sensors. Originals were still good but I threw them away about 6 mths after installing these.

Maybe fuel pump? I'm guessing its original.

I don't here a vacuum leak. Wouldn't a leak cause both bank to be lean ( codes P0171 & P0174).?

should I swap the o2 sensors side to side and see if the code changes to P0174 (bank 2)????

I borrowed a code reader and can see the various live engine data. But I don't know what normal is vs abby-normal?

 

[blackelky]

You want to sell that autocal ?lol

 

[Fless]

Document both the short- and long-term fuel trims at idle (both banks), then again at 1500-2000 rpm.

Also, after warming up a bit and going into closed loop, the upstream O2 sensors should be switching between 0.1 and 0.9v fairly regularly, especially if you vary the rpms. If your scanner will graph it will be easier to see the movement.

Could be a bad injector, exhaust leak, or a single bank vacuum leak, among other things.

 

[iamdub]

2007 Yukon Denali 6.2L L92 w/192k miles.
Past couple of weeks I keep getting the check engine light and code P0171-Fuel System Lean Bank 1.
No Mis-fires. Vehicle runs great, getting good mpg as usual, no other issues.
so
I ran a can of SeaFoam, no change.

18 mths and 18k miles ago installed 4 new amazon GM Genuine Parts O2 sensors. Originals were still good but I threw them away about 6 mths after installing these.

Maybe fuel pump? I'm guessing its original.

I don't here a vacuum leak. Wouldn't a leak cause both bank to be lean ( codes P0171 & P0174).?

should I swap the o2 sensors side to side and see if the code changes to P0174 (bank 2)????

I borrowed a code reader and can see the various live engine data. But I don't know what normal is vs abby-normal?

As @Fless said- scan and graph it. If your scanner will only display it, you could record it with your phone. Then swap the left and right sensors and scan it again. Hopefully the problem follows and you just have a defective sensor.

This just made me realize something: I've gotten (IIRC) the same code maybe three times since the engine work in 2020. I think it only happened after long drives. Swapping the sensors yielded no change. Just about 13 months ago, I had the intake manifold and LH cylinder head off to replace an exhaust valve after a valve spring broke. Since then, I've been on trips to New Orleans (2 hours one way), Galveston (5 hours) and south of Tampa (11 hours). Haven't seen that code, or any code, since that repair work. I wonder if I had a slight intake gasket leak that was corrected when I removed and reinstalled the manifold. I reused the gaskets since they were only 18K miles old.

 

[j91z28d1]

what are the long term fuel trims 1 vs 2 while driving like you were when it set.

I see over over that a tech 2 will show you the snap shot data recorded while the code was set. while I know the ecm saves this, I've never been able to access it. if you can find a scanner that will, or a listing I've missed, that should tell you what you need to know.

 

[j91z28d1]

not your exact truck, but to give you an idea of what the ecm perimeters look like for setting that code.

 

[donjetman]

Replacing the purge valve:
https://www.tahoeyukonforum.com/thr...e-w-o-driveability-issue.130243/#post-1726343

 

[donjetman]

I think I found the P0171 problem?

11/17/23
MILEAGE today– 191,577
Found air intake hose had popped loose. I last tightened it on 8/21/23 @ 190,200 after cleaning MAP sensor.
So, I spray cleaned the MAP sensor and reconnected hose.
Cleared P0171 code.

 

[iamdub]

I think I found the P0171 problem?
View attachment 414421
11/17/23
MILEAGE today– 191,577
Found air intake hose had popped loose. I last tightened it on 8/21/23 @ 190,200 after cleaning MAP sensor.
So, I spray cleaned the MAP sensor and reconnected hose.
Cleared P0171 code.

*MAF sensor

and

 

[Fless]

Theoretically that should cause lean codes on both banks, but time will tell Good catch!