code P0171
Thread Starter
Instructor
Joined: Sep 2011
Posts: 218
Likes: 5
From: Charlotte NC
code P0171
Hey, guys I have been getting this code P0171 system too lean (bank 1) on my 96 LT-4. The car seems to run great, and I'm trying to find what this is in the FSM. But I'm not having any luck so far. Can someone chime in and give me clue. Any help would be great. Thanks in advance.
Pro
Joined: Mar 2013
Posts: 628
Likes: 13
From: Indiana
Several things can cause a lean problem. An air leak after the air flow sensor, a bad injector, and weak fuel pressure are a few. Bad fuel pressure would/should show up on both banks. It is rare for an air leak to only show on one side but could happen. The most likely would be an injector or two on one bank being bad. The other item that affects one side is a bad O2 sensor. Since the car runs fine I would narrow it down to the O2 sensor on bank 1 side. The rear pair are only for smog checking and are not used in any way by the computer so it would be the front one that's bad. If you have not done it yet I would replace the injectors and O2 sensors. They should be done every 50k miles. It should clean things up fault wise but you will be happy with the improvement in gas mileage and performance even if it doesn't. Another thing that should be looked at/replaced is the PCV valve and hoses. These are maintenance items and like plugs and wires should be serviced on a regular basis.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
In addition to Klyde's informative post, read post #2 in the following
link...... may help (?):
http://forums.corvetteforum.com/c5-t...171-p0174.html
link...... may help (?):
http://forums.corvetteforum.com/c5-t...171-p0174.html
Melting Slicks
Joined: Jul 2008
Posts: 2,269
Likes: 142
From: Ottawa Ontario
Drifting
Joined: Jul 2004
Posts: 1,354
Likes: 291
From: MA
I think I remember one of my friends having this code on his fairly new back then LT4 Vette. They traced it to a bad diverter valve.
But obviously don't just change parts. Make sure it is bad before replacing it. I think the valve ruptured internally and allowed excess air into the exhaust stream (if I remember correctly it was 17 years ago).
Good luck let us know what you find.
But obviously don't just change parts. Make sure it is bad before replacing it. I think the valve ruptured internally and allowed excess air into the exhaust stream (if I remember correctly it was 17 years ago).
Good luck let us know what you find.
Thread Starter
Instructor
Joined: Sep 2011
Posts: 218
Likes: 5
From: Charlotte NC
Wow! Thanks for all the possible causes. I will look into the cheapest first. May daily driver needs help also. I will post the cure when I find it. I think it may be the MAF because I was getting a MAF malfunction before this new code
Thread Starter
Instructor
Joined: Sep 2011
Posts: 218
Likes: 5
From: Charlotte NC
I had the maf sensor cleaned and the lean code seems to be gone. However the maf malfunction is back. I clear the code and it is back as soon as I crank the car. The first few time I cranked the car it sort of stumbled upon cranking. Normally it will turn twice and start immediately, but this was only for the first few times. I'm going to look into a new sensor.
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Drifting
Joined: Jan 2002
Posts: 1,606
Likes: 1
From: Las Cruces NM
One of my lt4s had the same code and it was the intake gasket. Other areas for air to get in and affect one side are the injector o rings at the intake.
To determine if its a vac leak or sensor, you really need a scan tool to look at your O2 values and the corresponding bank's injector pulse/ block learn values.
Otherwise, you're sort of throwing parts at it hoping you hit the right one.
To determine if its a vac leak or sensor, you really need a scan tool to look at your O2 values and the corresponding bank's injector pulse/ block learn values.
Otherwise, you're sort of throwing parts at it hoping you hit the right one.
Thread Starter
Instructor
Joined: Sep 2011
Posts: 218
Likes: 5
From: Charlotte NC
I unplugged the maf sensor and cleaned it out. So far I've driven about 400 miles and no check engine light. I still have my fingers crossed but, as soon as I fix my daily driver I can get the intake, and valve cover gaskets replaced, as well as looking for other leaks.
Thank you all for the detailed advice, I wrote it all down for future reference.
Thank you all for the detailed advice, I wrote it all down for future reference.