Soooo, I've encountered the P0171 CEL about a dozen times now. This is the code for "Bank 1 O2 Sensor A/F Too Lean." The car is a 2002 WRX and the mods are as follows:

USDM Legacy GT EJ255 engine swap
SSAC top mount intercooler
UR EWG uppipe
TiAL 38mm EWG with dump tube
VF39 with welded flapper
Jet-hot coated Bosal twin dump downpipe
EcuTEK custom flash
Seimens 660cc injectors
Walbro 255lph fuel pump
Stock manifold and '05 catback

The code comes and goes as it pleases, wrecking my gas mileage while it's on. I recently made Davenow's grounding kit and it stopped the CEL from coming on for a longer period of time. Also, my soldering points were very poor and I need to redo it (bought a 50/50 flux solder from Home Depot which was crap). Could it be the grounds on the car just being crappy? I have 104k miles, about 13.5k since the swap and about 5k since I first encountered the CEL.

I really don't wanna drop $150 on a new sensor if it's not the problem, but I'm thinking I might have to. I looked at the thread with the nine possibilities for the CEL, but I have no way to pressure test my intake tract and after just being retuned I'm doubting that would be the problem.

It does come on while I'm cruising on the highway while in vacuum, so I am assuming it's a closed-loop fueling issue? Correct me if I'm wrong, OP/CP stuff confuses me.

Thanks in advance for any help,
Chris

can your tuner turn off the cell?

I can turn that code off for you Chris. Could also be a dead sensor too, with 105k miles its probably about time to replace it.

I can turn that code off for you Chris. Could also be a dead sensor too, with 105k miles its probably about time to replace it.

James, do you just turn the CEL off and have its effects still take place (the crappy mileage I get when it's on) or do you have the ECU completely ignore the sensor?

I'm confused how you do this when I have Ecutek; I wasn't aware that anything else could be done. I'll be home over Thanksgiving break (Nov. 20) where I need to bring my car to KTR and have some Cusco motor and tranny mounts installed along with a 3 port BCS, and then Ben is retuning the car. I'll ask him if he can tune out the code; if not I'll swing down into CT and have you do it.

- Chris