CEL code P0171 System Lean
 

I have an 08 X with ~2,000 miles. I recently installed an AMS intake and uicp. Car runs good for about a week or so then I get the cel. When I scanned the car I got error code P0171 system lean.

I checked everything to make sure nothing is loose etc.. but everything seems fine. Car runs great no signs of issues other then the cel.

I have searched and it seems like most people that have gotten this cel have a tune of some kind. I am 100% stock besides the intake and uicp. I was told it may be a dirty MAF sensor but the car has 2,000 miles I just find that impossible to believe. I did reset the code once already drove for ~50 and the light came back on. I was driving at almost wot when the light came back on for what it's worth.

My plan is to put back on my stock airbox reset the code and see if it comes back on. I was hoping someone could save me some time and tell me wth is going on.

I would appreciate any thoughts on this.

Well, most intakes actually lean out the air fuel mixture from not only the higher flowing filter element, but but by using a larger diameter maf housing that through increased diameter, actually reduces velocity over the maf. This in turn tricks the ecu into running a lower load cell, and lower load cells run leaner air fuel ratios and more timing. This will increase power, and on a stock tune where the air fuel ratios are super rich, is usually safe. This could certainly contribute to why you are getting that code, but many people with similar setups don't.

I feel the need to let you know though that once you are tuned, unless you are at extreme power levels, intakes don't make any power over a stock box with a drop in. This is because the air fuel ratios will be properly adjusted and the overly rich condition through which the intake makes power on will no longer be there. You'll still gain plenty of power from the tune by further leaning out the a/f ratios, increasing boost, adjusting mivec, timing, etc but again, unless you are extreme power levels where the stock box becomes a restriction, the intake is a waste of money.

But anyway, going back to your initial question... I have not heard of anyone running into this cell that was tuned (tuned properly, at least). The most common code is a P1235 code (most common with MBC users), and the ASC service light popping up randomly during spirited driving. Anyway, good luck; I wish I had more helpful information.

^ Great info in this post thanks.


The downside is I still am unsure why I am getting this code. I understand the difference in airflow etc., but it still makes 0 sense to me. I can't be the only untuned GSR running around with an intake. I can't understand why I get this code and many others do not.

I have the same exact set up as the OP (AMS UICP and Intake with heat shield) and i sometimes get a CEL. What CEL it is I don't know, cause I normally don't have the time to take the car to autozone to get a CEL reading. All I do is diconnect the battery for 30 minutes or so and the CEL goes away. Sometimes it takes weeks for it to come back on. It took a month for the CEL to come on after I installed the intake.

Now whether or not its a lean CEL, I don't know. Next time it happens again, I will be sure to go by autozone.

But just FYI, my CEL comes on under normal driving conditions. I'm not beating up on the car or anything.

JDW1479 if you were closer to me I have a code reader and could pull it for you.

damn man yeah you may want to get that code scanned. Better to be safe than sorry. My code is system lean in bank 1 and I certainly wouldn't want to drive around like that.

what a PITA trying to find the reason for this.

My first step is to clean the maf sensor if that doesn't work then I will put back in the stock intake, and if that doesn't work it goes into the dealer.

Well .. actually .. that is not true ..

You will end up with lower gains after a tune compared to an aftermarket intake without tune only .. but you will still gain more hp after tune with intake versus after tune without intake.. in the region of 7-15hp ..

This is no longer the karman sensors of fore .. there is no change in frequency with a change in intake like a dropin or a KNN pod filter.. UNLESS you are talking about changing the size of the intake piping .. that changes the calculation and affects the load calculation ..

The leaner AFR you guys actually see is from the increase in airflow .. not from the change in computation (like the older Evos)


For the OP .. here's a couple of things you can check before you fix back stock ..

Fuel press regulator vacuum line (I've seen quite a few popped off) from the intake manifold side

improper fitment on the intake (ie leaks / crimped rubber) leading to leakage allowing air post MAS to enter .. this leads to more air than measured and your lean condition ..

Can I know what size is the intake piping ?? ;)

I already cleaned the MAF sensor this last time, which was a couple of days ago. Really didn't see any K&n oil on it. It was pretty much as dry as a bone. I have no idea what could be happening. But I'm sure Goofy will help me out later with the scanner.

K.I.S.S.
You changed out your intake for one that flows more air.
You then throw a CEL indicating you're too lean. Your ECU can compensate up to a point, but a re-map is recommended any time you make a change to any system (intake and exhaust) that changes flow.
Put it back to stock and see if it stops throwing the code.

take off any high flow filter or intake, or have the car retuned

intakes on a X is a waste of money unless your untuned. Even a drop in is not worth it. I got my car tuned, installed a k&n drop in and made another pull and got 0 GAINS

I think this nonsense has to stop .. if you're using piggybacks .. that's a limitation of the piggybacks .. if you're using reflash of anykind .. you WILL GAIN ..

I had the same issue when I first got the AMS Intake. I bought the one that had the bungs for the breather and the Boost controller. I ended up tighting the breather hose with with some clamps because it seemed loose with the factory tension clamps and have not seen the po171 since. Thanks Chris at AMS for helping me out. Hope this help any of you guys/gals. CJ

Hmmmm I would like to hear more about this. I think this maybe my problem too after ruling basically everything else out. The tension on my stock breather hose is so much that it is slightly pulling up on the rubber grommet AMS attaches the breather bung to the intake with.

I can't figue out why the breather bung isn't welded on like every other intake I have seen. By using the stock hose it just doesn't seem like the best option.

My question is if the breather bung grommet is leaking air (potentially) would this cause a P0171 code?

I would assume that it would due to the unmetered air. Who else has an AMS intake and did you buy a new hose or use the stock one and if so is your breather bung flush with the intake?

Cel P0171
 

Gents I have the same proble first i had the EGR Code P0401 so I checked all the hoses and i had one lose. So i fix them by putting zips on them problem solve. Now i get this code p0171, Im going to check the MAF sensor. But can the Gas make this code to appear if the vehicle was tuned for 91octane and I fill my car with 93 dont know need help and can i still run the car like this or it will cause damage.

The Other question is that my ANTI lock light came up and the code is 82 ST-2 open circuit can someone help me with this before i take the car to the dealer and they rip me off like they normaly do to us evo owners.