Hey everyone. Just wondering what I should check for besides dirty air filter and MAF if I come up with a P0171 - system too lean code? My wifes 02 Pro just gave her this CEL the other day. At the same time the weather dropped to like -25. Would that have done anything? Any help would be great. thanks

 

P0171: Fuel trim system too lean
Causes: misfire, malfunction of O2 front sensor, PRC solenoid valve, pressure regulator, fuel pump, purge solenoid valve; fuel filter clogged or resticted, fuel line leakage, fuel return hose clogged, leakage from exhaust system, insufficient compression.

 

thanks Krayziefox. I'll check those other things. Where's the fuel filter located anyways? I can't seem to find a Haynes manual for my car anywhere. It seems they don't make one for a 2002 Pro. How would I purge the solenoid valve?

 

The fuel filter is inside the fuel tank itself. They're usually not a problem tho, since they're designed to be good for the lifetime of the car. Check http://protege5.ugly.net for the Haynes manual .. we don't have a printed version offered to us but the website is just as good (probably better).

 

Yeah, air filter clogged causes the car to run rich (not lean).

 

you need a fuel strainer for the bottom of the pump pickup....very cheap, very easy job.

 

my bet would be 02 sensor

 

Thanks Krayzie Fox. That protege5ugly site is great for an online manual.

Hey Roddimus. Where would I find a fuel strainer for the bottom of the pump pickup? Can I just walk into any parts store and ask for a fuel strainer and they'll know what I'm talking about? What's all involved with installing one? Will I need to take the gas tank off or anything major like that?

As for the O2 sensor, how do I go about checking to see if it's that? How can you test to see if it's working right?

 

I'll look one up when I get to work and let you know how available it is. to instal it you just pull up the rear seats and go into the gas tank from the flap in the carpet. Unscrew the hanger assembly and the strainer sock will be hanging from the bottom. Pop it off and clip on a new one.

 

^think that could by my same problem, gas cuts out when tank is < 1/4 full

 

Me? If it was either one - i would swap the O2 sensor first (easier). And it will clog eventually anyway - so it is not a wasted effort.

 

are O2 sensors expensive?

 

Nope, usually $40 or so.

EDIT: Ok it turns out they're a little bit more expensive at $65 - $75 each, O'Reilly's Auto seemed to have the cheapest one available (Bosch Universal). Advance, Auto Zone, and NAPA were all in the $150+ range. Send a PM to Roddimus Prime, I remember him saying something about being able to hook us up with cheap replacement parts so see if he can help ya out at all. Good luck!