PO171 Problem - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-08-2010, 09:48 AM   #1
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Cool PO171 Problem

Just for info, I have been combating a PO171 code in my 1997 SSE for the alst year. I have checked all of the engine factors for vacumn leaks, ran the General Motors Fuel addative for two taks of gas to clean all sensors. changed the oxygen sensor, cleaned the MAF, and changed the fuel tank Caps (two times). The light would stay out from 3-4 days after clearing it, and sometimes would come right back on within 30 minutes. Sometimes it would go back off by itsself a couple of time in a couple of days. I could not figure out what was cusing it. (Too Lean Bank 1).
Well, yesterday, I found a vacumn canister under the right front fender that had a small cap with a tiny nipple that that vacumn hose connected to. It was cracked . I replaced it and cleared the code. So far, it hasn't come back up. Of course it might within the next couple of days. Just wanted to give the info incase anyone else might be experiencing the same repeated code to check that cannister connection. Thanks,
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Old 01-08-2010, 09:59 AM   #2
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That vacuum canister is for the HVAC system and is fed on the SC models from the vacuum port on top of the SC. The NA models have a vaccum connector next to the hose for the brake booster where it gets vacuum at the manifold.

Good find. If you have further issues with the code, I'd suggest looking closely at your battery cables.
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Old 01-08-2010, 10:03 AM   #3
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Thanks, I have had problems with the HVAC Modes also, so I did notice this morning that the modes were also working correctly. Thanks for the info!
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Old 01-08-2010, 11:01 AM   #4
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That'* the problem with that code. Vacuums leaks are the cause most of the time. The HVAC is harder to check because it'* more hidden and goes clear back to the fuel tank. Good find.
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Old 01-08-2010, 11:21 AM   #5
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Quote:
Originally Posted by Danthurs View Post
The HVAC is harder to check because it'* more hidden and goes clear back to the fuel tank. Good find.

Fuel tank, HVAC?? Dan do you mean vacuum is sometimes tough to trace because it spans from the tank and all over the car?
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Old 01-08-2010, 11:24 AM   #6
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It'* forgotten about. Most people check the lines on top the engine and forget the rest.
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Old 01-08-2010, 11:29 AM   #7
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True..the engine bay is where 97%ish of them are though. But then if there'* an evap line issue, it will add an evap code and send you down a different solution path.

A simple P0171 ....well, let'* say once you get the code and start trying to fix it. You learn quickly it'* probably the meanest code in the PCM. In my case I chased every ground, every vacuum line, changed maf'*, checked gaskets over and over etc. Found out that corrrosion in the battery cables can cause enough of a power issue to trigger the system into seeing readings and triggering the code. Reading that I couldn't see on the scan tool. Three months of fighting teaches us many lessons and gives a guy many places to look for vacuum leaks. Another that is typically overlooked is the EGR tube from EGR to LIM. It doesn't trigger an EGR code.
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Old 01-08-2010, 12:01 PM   #8
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Good info guys, I should have put this question on here along time ago. I looked all over the engine on top as stated. Hopefully this is a fix.
Thanks again.
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Old 01-09-2010, 01:17 AM   #9
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Moved to Mechanical 92-99 for better visibility and search indexing. Lets get some tags in this please.
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Old 01-11-2010, 09:13 AM   #10
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This one just popped up one me yesterday. Out of the blue. I had it read at Autozone and was surprised at how many issues it could be just for one code.

Anyway, what'* the first thing that should be checked with this code? Clean the MAF?
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