OBDII code P0171

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bajablacksheep
Scoobytruck Lurker
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Joined: Fri Jul 31, 2009 4:00 pm

OBDII code P0171

Post by bajablacksheep »

Engine light came on the other day. I have an OBDII code scanner (if you ever need one you can go to places like Autozone and they will plug in and give you the codes for free) so I hooked up and got code P0171. This is an o2 sensor lean condition. I'm just a shade tree mechanic and once upon a time I would have tried changing the o2 sensor, but I've learned it's never that simple. This just means the o2 sensor is probably doing it's job and telling you something else is causing the lean condition. Lean= too much air or too little gas. Possible causes would be clogged fuel filter, clogged injectors, leaking intake manifold, broken or disconnected hoses (this has happened to me on other cars will make it run really bad, great relief to think you have a big problem and end up just reconnecting a line and everythings back to normal) or other sensors are faulty (typically the MAF, mass air flow sensor in the air cleaner).
First I gave a quick look under the hood and poked around to make sure no rubber hoses were obviously broken or disconnected. Looked good as far as I could see (so hard to see anything in this car).
Next I figured the car has 36,000 miles and should be due for a fuel filter. Looked in my Subaru Haynes manual and found out the only fuel filter for the turbo is in the gas tank. Decided to come back to this option if other checks didn't fix it.
Next I pulled out the MAF. Really easy as it is right up top on the intake snorkel where the air filter is. Just one electrical connector and two screws. Pulled it out and sprayed it with electical contact cleaner and put it back in. Erased the computer codes and took it for a ride. Voila! It's been 4 days, many trips, and a couple hundred miles. Still no pesky check engine light. Fixed in a matter of minutes for $0.
the slug
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Location: North Metro Atlanta

Re: OBDII code P0171

Post by the slug »

Congratulations! Nice to see that somethings are simple fixes on "newer" cars.

Yeah, I don't envy the fuel filter change on the turbo models. Mine is out in the open in front of the firewall, lol.
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Sometimes I have a full tank of gas.
bajablacksheep
Scoobytruck Lurker
Posts: 9
Joined: Fri Jul 31, 2009 4:00 pm

Re: OBDII code P0171

Post by bajablacksheep »

My understanding is that the non-turbo models have the external underhood filter AND the filter in the tank. I imagine the in tank filter is just the "sock" attached to the pickup/fuel pump like in every car I've had the "pleasure" of putting a new fuel pump in. There's even a "sock" in the tanks of old cars that had the fuel pump attached to the motor.
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