P 0171 Code
Thread Starter
Melting Slicks
Joined: Feb 2008
Posts: 2,977
Likes: 4
From: Delmar Delaware
P 0171 Code
Anyone have any experience with this code? A few times in the last few days I have been driving on the bypass and my car seems to shift out of OD. 30 or 40 seconds later,I get a code that is P 0171. I researched the code but don't understand why the car would be doing this. Only other thing I've noticed is a loss of fuel mileage.
Safety Car
Joined: Jun 2006
Posts: 3,787
Likes: 2
From: Wildomar CA
You have one of the following problems
Loose intake tract.
Dirty Maf
Bad 02 sensor
Vacuum leak
clogged fuel filter
clogged fuel injector
and many others...
Start with the loose intake and clean the maf, that will probably fix it.
p0171 is a lean condition at the 02 sensor
Car thinks it is going lean (too much air) so to compensate it adds more fuel
more fuel = bad mileage 
Loose intake tract.
Dirty Maf
Bad 02 sensor
Vacuum leak
clogged fuel filter
clogged fuel injector
and many others...
Start with the loose intake and clean the maf, that will probably fix it.
p0171 is a lean condition at the 02 sensor
Car thinks it is going lean (too much air) so to compensate it adds more fuel
more fuel = bad mileage
Burning Brakes
Joined: Mar 2010
Posts: 1,189
Likes: 4
From: Freeport, FL
Sounds like the code indicates that it is lean in bank 1 which may indicate that it could be too much fresh air reaching only the bank 1 O2 sensor. A misfire from a bad plug on bank 1, an exhaust leak on bank 1, something that would only affect bank 1 though.
Could be many things though. Good luck
any other codes showing up?
Could be many things though. Good luck
any other codes showing up?
Safety Car
Joined: Jun 2006
Posts: 3,787
Likes: 2
From: Wildomar CA
Good point. I always forget when I am dealing with an eight that it should accompany a bank two code as well.
Check the tightness of your exhaust manifolds and check for leaks. You may also have a bad fuel injector on that side if it only throws the p0171. Might also check the bolt tightness on the intake manifold and make sure they are all torqued to spec.
Could also be that 02 sensor went bad as well. The one side code should help narrow it down though. Sorry I didn't even consider bank two. I was still thinking inline four since I just had the same problem pop up on my wife's beetle.
As of yet I have yet to actually fix it. I believe the bank 2 code is a 174. Let us know how it goes.
Check the tightness of your exhaust manifolds and check for leaks. You may also have a bad fuel injector on that side if it only throws the p0171. Might also check the bolt tightness on the intake manifold and make sure they are all torqued to spec.
Could also be that 02 sensor went bad as well. The one side code should help narrow it down though. Sorry I didn't even consider bank two. I was still thinking inline four since I just had the same problem pop up on my wife's beetle.
As of yet I have yet to actually fix it. I believe the bank 2 code is a 174. Let us know how it goes.
Burning Brakes
Joined: Jan 2010
Posts: 763
Likes: 0
From: Murfreesboro TN
I read in the 1999 C5 GM Manual for a little while tonight...
It sounds like what was mentioned above and your issue is related to one side otherwise you would have gotten the P171/P174 codes.
This narrows it down to an injector, exhaust leak or bad O2 sensor or other issue common to bank #1.
You might want to swap the driver's side sensor with the passenger's side sensor (move the sensor and swap plugs) to see if the code clears and the P174 code comes in.
If the problem moves from bank #1 to bank #2, you have a bad O2 sensor.
If the code P171 returns or doesn't clear, you have an injector issue or exhaust system leak on bank #1.
It sounds like what was mentioned above and your issue is related to one side otherwise you would have gotten the P171/P174 codes.
This narrows it down to an injector, exhaust leak or bad O2 sensor or other issue common to bank #1.
You might want to swap the driver's side sensor with the passenger's side sensor (move the sensor and swap plugs) to see if the code clears and the P174 code comes in.
If the problem moves from bank #1 to bank #2, you have a bad O2 sensor.
If the code P171 returns or doesn't clear, you have an injector issue or exhaust system leak on bank #1.
Last edited by TN Vette; Nov 13, 2010 at 10:56 PM.
Thread Starter
Melting Slicks
Joined: Feb 2008
Posts: 2,977
Likes: 4
From: Delmar Delaware
Thanks guys. I Seafoamed it yesterday to try to clean the injectors and what not. I do get an occassional P 0492 code which I believe is the passenger side AIR system trouble code. I'm going to work on this today and hopefully get things resolved. Thanks again.
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Le Mans Master
Joined: Jun 2007
Posts: 6,301
Likes: 6
From: LAND OF OZ Kansas
I read in the 1999 C5 GM Manual for a little while tonight...
It sounds like what was mentioned above and your issue is related to one side otherwise you would have gotten the P171/P174 codes.
This narrows it down to an injector, exhaust leak or bad O2 sensor or other issue common to bank #1.
You might want to swap the driver's side sensor with the passenger's side sensor (move the sensor and swap plugs) to see if the code clears and the P174 code comes in.
If the problem moves from bank #1 to bank #2, you have a bad O2 sensor.
If the code P171 returns or doesn't clear, you have an injector issue or exhaust system leak on bank #1.
It sounds like what was mentioned above and your issue is related to one side otherwise you would have gotten the P171/P174 codes.
This narrows it down to an injector, exhaust leak or bad O2 sensor or other issue common to bank #1.
You might want to swap the driver's side sensor with the passenger's side sensor (move the sensor and swap plugs) to see if the code clears and the P174 code comes in.
If the problem moves from bank #1 to bank #2, you have a bad O2 sensor.
If the code P171 returns or doesn't clear, you have an injector issue or exhaust system leak on bank #1.
Yeah, I had forgotten that I did get both 171-174 codes.
Thread Starter
Melting Slicks
Joined: Feb 2008
Posts: 2,977
Likes: 4
From: Delmar Delaware
Thanks Z06. After the Seafoam,the code hasn't returned for 2 days (it's my daily driver) but the gas mileage isn't even close to normal. It's about 5mpg off normal on the highway and 3-4 mpg off on average.
Safety Car
Joined: Jun 2006
Posts: 3,787
Likes: 2
From: Wildomar CA
Might be time for a full tune up then. Possible you had a cloged injector and the increased fuel may have gummed some stuff up being rich. Try taking out some of the easy to reach plugs and report on how they look. Plus also remember it will take your car some time to relearn in order to maximize efficiency again.
You might be best off resetting everything to factory by disconnecting both battery terminals for like an hour. See if things get better after that.
You might be best off resetting everything to factory by disconnecting both battery terminals for like an hour. See if things get better after that.
Thread Starter
Melting Slicks
Joined: Feb 2008
Posts: 2,977
Likes: 4
From: Delmar Delaware
Going to order the plugs and wires this week. Cleaned the MAF tonight with no effect. Haven't seen the code in a couple days but fuel mileage is still bad in comparison.
