P 0171

[NJTB]

Anybody have the GM troubleshooting guide for a code P 0171?
Checked the search function here but didn't find the solution. I did check what was mentioned (vacuum leaks, fuel pressure, etc.). There was even one member that fixed it with an SAIS valve. So I'm stuck and hoping to get the page from the manual with the diagnostic procedure on it.

 

[Blackstar]

P0171 code from my Chilton repair manual is "System too lean, left bank".

 

[Blackstar]

Have a look here.. https://www.google.ca/search?ei=Ee_......0...1c.1.64.psy-ab..0.0.0....0.O3vI67uvkJE

 

[xavierny25]

www.google.com/search?ie=UTF-8&client=ms-android-hms-tmobile-us&source=android-browser&q=P0171+gmtnation.com

Pick a thread to read through and I'm sure you'll figure it out....
Our search on the forum itself isn't the best.
when searhing I use Google (doesn't matter what you use) and add gmtnation.com to the end of what info I'm looking for regarding our trucks (360's or 370"s).

 

[Mooseman]

This is how you do it

http://lmgtfy.com/?q=p0171+site:gmtnation.com

 

[NJTB]

Thanks all. Heading out to the garage now, will let you know how I make out.

 

[budwich]

From some reads in the past, it appears that you may have done some of the things (although your description is thin so it is hard to say). From those reads, if you have access to some data device (ie. torque), monitoring your fuel trims at idle and at various rpms may provide clues as to where to look. Higher readings at idle may high light a "significant" leak around intakes somewhere since the vacuum is high... what is your idle rpm reading? Higher readings at high rpm would probably place the leak else where.... exhaust or otherwise. Have you monitored the o2 signal output? Further, when was the o2 sensor last serviced / replaced? Have you had any loss of coolant in recent times? Hopefully, you can find the issue before your cat gets ate...

PS... quick search shows "For heated sensors, normal deposits are burned off during operation, and failure occurs due to catalyst depletion. The probe then tends to report lean mixture, the ECU enriches the mixture, the exhaust gets rich with carbon monoxide and hydrocarbons, and the fuel economy worsens." Hence, the question about the service life of the sensor in question.

 

[NJTB]

It went like this. For 3 days, the P0171 was there, idled at 900, and couldn't clear it with the scanner. I went out, started it up, the code went away, the idle dropped and all was well. Piss me off.
At any rate, since it cleared itself, I'm looking for a bad component (SAIS, O2 sensor) or something like that. I don't think it's loose manifold bolts as it idles like glass. Going to monitor the fuel trims and make sure I don't have a 'lazy' O2 sensor, etc. The O2 sensor was replaced in 2014 with an AC Delco, there's about 20,000 miles on it.
I'm also torn if I should just replace the SAIS valve. Hate to spend the money and throw parts at it) on it but how do you check if it's intermittently sticking? Again, it was replaced about 3-4 years ago with an AC Delco. That design is truly a POS.
Thank you all for the time and effort you put in to help me out.

 

[budwich]

The sais may be a culprit. I think you can unplug it and see / wait on the outcome for a bit (ie. no p0171)... but of course, you will get other codes associated with the unplug ... and then go from there. To me, your high idle suggests issues towards the "front end of fuel air" but the sais is one component that can dump significant air into the system (unmetered) at any time that it "barfs".

 

[Mooseman]

I'd delete the SAIS and get the codes deleted with a tune. SAIS is a trouble prone system that does little to reduce emissions. Not worth the money. And you also get the benefit of the tune. And as noted in one of the threads, he's had multiple failures of the same valve.
Removing Secondary Air Injection System
Air Check Valve delete parts: GM 2574378 & GM 24577193 ...
SAIS gasket (Reasons to delete SAIS and tune)

 

[budwich]

one other data point to check is vacuum at idle now that your system appears to be "functioning". This will give you a "benchmark" should things go south again... plus if there is no change in the good and bad... that you can move away from a vacuum leak issue to some where else like the exhaust area. check vacuum at idle and at say your 900 rpm so that you have a couple of points for good and bad.

 

[NJTB]

Budwich, I like the way you think, and yes, that's a real good idea and I'm going to do it.
Mooseman, in post #5 you sent a link I clicked on. When the mouse pointer started moving by itself, it scared hell out of me, didn't know what was happening. Just my mad computer skills.
For a test, does anyone think it's possible to fabricate a block off plate for the SAIS valve and put the valve back on? Will it screw anything else up?

 

[Mooseman]

You could make your own easily with steel plating on it's own or a piece of sheet metal sandwiched with a second gasket with the valve. I'd just delete the whole thing unless you have issues with it passing a visual e-test.

 

[paul2005tb]

I started getting the P0171 code, did some reading youtube watching and found the little nipple on intake manifold-resonator just inboard next to the intake manifold resonator. That nipple was a bit worn, I took some RTV silicone rubber and filled it up and stuck it back on. Three days later and 100 miles and it has not re-thrown the code. Im not certain Im out of the woods yet on this one.

By the way, once you get a price on replacing the SAIS you are going to go back and read Mooseman's comment about the delete and tune. That SAIS is one rube goldberg octopus system that will strangle you if you try to keep it working. No idea how that monstrosity of a system was approved at GM headquarters.

 

[Mooseman]

Would you happen to have or can get a pic of said nipple?

 

[paul2005tb]

This is the OEM nipple (I guess it could be used for checking for air leaks but otherwise is of no use).

Suspect that after 13 years heat caused it to weaken and loosen. Probably best to replace it but this was my quick solution.

 

[Mooseman]

Ah yes, that's the one used by extended trucks for the rear hvac. Otherwise it's either plugged or it's not drilled out inside. Good to know to check on it.

 

[paul2005tb]

I cant see how that port to the intake manifold would have any use for any hvac system , rear or otherwise ?

 

[budwich]

vacuum "valve" operation?

 

[NJTB]

When I first posted this the P0171 code was there for 2 weeks, a hard code I couldn't clear. So I did a search here and checked the things that were mentioned, making sure the intake bolts were tight, etc. Then the light just went off, and now I can't get it to come on again. This tells me it's a component, and I'm real wary of the SAIS valve, that I'm probably going to block off the next time the code appears.
Understand, this car doesn't get driven much, I bought it in '08 with 30,000 miles, now it's got 130,000 on it, and the vast majority is highway miles.
I'm still fighting with it, but not real confident I'm going to win.

 

[Mooseman]

The SAIS is one of the most trouble prone systems ever devised, right next to the EV fan clutch. I'd dump it now as a preemptive measure.

 

[tyler]

Trying changing the purge valve, this fixed my p0171 problem. Sais are pain in the ass

 

[NJTB]

That's a part I'd throw at it, cheap and not too bad to replace.

 

[mrrsm]

https://gmtnation.com/forums/thread...p-system-test-never-passes.18075/#post-551244

 

[sunliner]

just curious did yours ever clear? I've been driving with this stupid code for four years now. Truck runs ok, just can't clear it

 

[NJTB]

The code just went away, and it's been running fine. Annoys the crap out of me that it's so intermittent. At least I know the intake bolts are tight and there's no vacuum leaks.

 

[budwich]

The code just went away, and it's been running fine. Annoys the crap out of me that it's so intermittent. At least I know the intake bolts are tight and there's no vacuum leaks.

NJTB... another data point for thought just in case your situation changes back to "bad". I just replaced my cracked exhaust manifold. I did a run to check things out for a bit and monitored my fuel trims. At highway cruising and warm engine, my LT trim was running basically at 0.0 where as before it would run at -2. - 3. ish ( not quite the same "test conditions" but the result 0.0 is more expected). Anyways, I hope your problem has disappeared for what ever reason BUT that you have taken note of the running / idle vacuum data along with fuel trims as suggested so that you have a "bench mark" for your vehicle that might help in the future, should it go south again.