P0171 error code

KEN JAMES

MEMBER
2005 NISSAN SENTRA
1.8L
4 CYL
2WD
AUTOMATIC
273,000 MILES

About a month ago the “check engine soon” light came on. I pulled the code and it comes up with a P0171. I read just about everything there is to read on the internet about the P0171 code and I am so confused now. So far I have changed the air filter, cleaned the MAF sensor, replaced the PCV valve, it was kind of gummed up, put a can of Sea Foam in the gas tank and checked all the connections and hoses. I can clear the error code drive the car all over town for days and the check engine soon light will not come on, when I get on the freeway it will come after about two or three miles of driving on the freeway. The car runs prefect and is in excellent condition. I am at a loss, I do not know what to do or direction to go in now, I am an old Vietnam veteran on a very fixed income.

Thanks for any help or direction you can give.

Randy
Tacoma, WA

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Three things are the main cause of the lean condition. First is an engine misfire I know you said it is running good put if you have not installed a new set of plugs in a while this is where I would start. Next I know you said you cleaned the MAF but most of the time they are too far gone to be cleaned and need to be replaced. Third is low fuel pressure from the fuel pump.

Here are a few guides to help us get started fixing the problem:

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

and

https://www.2carpros.com/articles/how-to-change-spark-plugs

and

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

Please run some tests and get back to us.

Cheers, Ken