CEL p0171

[rigo]

i have a 02 wrx. it has a Greddy inter cooler, k&n air filter and after market exhaust. i got the car about 7 months ago for the past 2 month a CEL (P0171)(running to lean bank1) had been on. i have change the 02 sensor the fuel/air mix sensor and and the spark plugs. i clean my MAF sensor and air filter and change my gas filter. i check for vacum line leaks and didn't fine any but the CEL keeps coming back on. i had a mechanic check the fuel pressure and he told me every thing is ok he doesnt know why the CEL is on. according to him the light should not be on every thing is working the way it should. the car runs great. if i clear the CEL it comes back between 20-30 miles after clearing it. can someone please help me or should i just send it to subaru.

[Timdog1650]

Did you pressure test the system? You changed both O2 sensors? The sensor that is throwing that code is the one in the passenger side exhaust manifold. The rear O2 sensor in the midpipe wouldn't register that code...what do you mean when you say the "fuel air mix sensor?" If I had changed every possible part and eliminated all possible "normal" reasons for a lean code, I would start to suspect the aftermarket mods. Is the K&N filter a full ram air intake or is it just a panel filter in the stock airbox? The intake could cause that code if there was something wrong with it or if it wasn't a WRX specific intake. If it's just a K&N panel filter, I wouldn't think twice about it because there's no way it could cause a lean code. I would also wonder about the intercooler...if you aren't tuned for a FMIC it would not be especially surprising that your fuel trims would be out of spec. That's about the limit of what I would know to troubleshoot without delving into the ECU via Tactrix cable... maybe Donkey or Testes1010 will reply to this with a more scientific approach.

[rigo]

yes the mechanic did pressure test it. the k&n filter is a ram air intake and it was made for a wrx. what's FMIC? and how do u tune and car for that. the fuel air mix sensor is the first sensor in the exhaust that what subaru called it.

[Timdog1650]

FMIC is "front moun intercooler".

[rigo]

it is a front mount intercooler how do u tune a car for a FMIC

[Timdog1650]

it is a front mount intercooler how do u tune a car for a FMIC

Electronic Engine Management. We have a separate subforum here that relates directly to tuning, you should take a look around and use the search function in there to better understand. Also, try taking a look at the links in my signature, they'll fill you in on some basics.

[EJ257]

Electronic Engine Management. We have a separate subforum here that relates directly to tuning, you should take a look around and use the search function in there to better understand. Also, try taking a look at the links in my signature, they'll fill you in on some basics.

Engine Management FAQ: Read if you are thinking of buying one! - NASIOC