I threw the Code P0171 a few times now, and iv seen a couple other on the forum who have thrown this code. P0171 is defined as (seeing OBDII code list) as System Too Lean Bank 1. But, what this really means is fuel pump = epic fail. mines gone now, and that's the reason.
The reason I think P0171 is a fuel pump code is because i was reading up on the parts catalog for our car in the maintenance section and it said when it comes time to mess w/ the fuel pump when removing it your car may throw Code P0171.
And this is not for installing a performance one this is simply for tinkering w/ the fuel pump.

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No, it means system too lean. Fuel pressure issues can be one cause of this.

The codes dont pertain to cause, they pertain to effect. Multiple causes can cause one effect (sometimes many concurrent causes.. and sometimes because of the systems reaction to other codes).

 

My P0171 was fixed by replacing the primary O2 sensor.

Throw that one in there.

 

but possibility of it being a fuel pump is up there, yeah fuel pressure makes sense.

 

I've had P0171 once.......it was because of a crap tune....adjusted my O2 map...everything's gravy.

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Yep.. like I said, anything that can cause the car to run lean can set the code. The ECU has zero idea why it is lean.. only that it is lean and it continues to run lean when the ECU adjusts. The ECU in most cases only tells you what is out of spec.. kind of like telling the doctor what hurts. The good troubleshooting is what tells you why

 

X2, I had the same issue

 

also could mean improper tuning, fuel trims.

 

aen did you not read my post....lol

 

for me replacing my fuel pump fixed this code...p0171 can be several things one being fuel pump.

 

Never mind I'm wrong, I changed the fuel pump and the code returned.....it's O2 sensor fosho

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There's a TSB on it on the 2005-2006 tCs. Stock O2 sensor may malfunction.

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can i roll up to toyota be like yo man fix it lol

u think thyll notice the boost lol

 

Nah - you're SOL there.

 

i just replace primary o2?

 

I think that's right Crayola...if it is the O2 sensor it would be the Primary O2.......good luck brethren

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Yep, second O2 is purely for CAT monitoring.