what could be causing these two codes???

**02silverbird** · 10-22-2010, 03:46 PM

Hey all
I was just wondering what could be causing to have these two codes pop up???

p0171 system too lean (bank 1)
p0174 system too lean (bank 2)

The car is running real good and the only things that have recently been done to it was the oil pan was replaced, the spark plugs were changed out, took off the screen to the air intake for better air flow, and I ran sea foam through it and changed the oil. I also changed out the PCV valve as well. So I don't think any of these things would create me having the codes but who knows... Also would re setting my PCM do the trick? Or would it have to do more with the changing of the PCV valve?
Any input would be helpful. Thanks all

**TokerM** · 10-22-2010, 04:04 PM

Lean codes... I've been getting them too, starting to chase it down.

Start by changing the fuel filter. That's one possibility.

I did that and my codes went away for ~200 miles, then came back. It was then that I found a vacuum leak on my PCV hose. That's what I have to fix next trying to chase this down.

Also try cleaning your MAF

In short, if it's running lean, it's not getting enough fuel, or mixing in too much air.

**02silverbird** · 10-22-2010, 04:12 PM

Hmmmm That is another thing that I did change as well was the PCV valve

**Cutlass** · 10-22-2010, 05:51 PM

If you de-screened your MAF...that could be the problem. The MAF is sensitively calibrated unit. Any mods to it(descreening, porting, deblading) and it throws the reading off.

**02silverbird** · 10-22-2010, 06:01 PM

Cutlass,

That's what I was thinking as well but the weird thing is that it never throw a code when I de-screened the MAF. I changed out the PCV valve and it didn't throw when I drove it home but once the car sat over night and I went and drove it the next day, that's when it thew the codes. Could that mean anything? Maybe a bad PCV valve??

**cammed goat** · 10-22-2010, 06:20 PM

Stock airbox or aftermarket cold air intake?

**Cutlass** · 10-22-2010, 06:22 PM

It can take a couple drive cycles to set codes. Doesn't necessarily happen instantly after descreening or PCV replacement.
But those lean codes can indicate a large vacuum leak. Maybe the PCV is defective and causing a large leak. Maybe the PCV hose is rotted and leaking.

**02silverbird** · 10-22-2010, 06:54 PM

Thing is that I have a 2002 3.8 and the PCV vale goes under the PCV plate on the plenum. So there is no hose. Any other way I could check?? I mean it didn't seem to do this with the codes untill I changed out the PCV valve. I took the MAF screen off about a month ago and drove it with no problem. It never threw a code. But I changed the PCV valve, changed the spark plugs, and changed out the oil pan (because it was rusting out) and the day after I did all that that's when the SES light went off

**02silverbird** · 10-22-2010, 06:58 PM

Originally Posted by cammed goat

Stock airbox or aftermarket cold air intake?

I have a SLP cold air intake tunnel, and a aftermarket lid, with K&N air filter. I did have to change the oil pan ot because it was rusting out so bad and they did have to drop the exhaust down. They did put in 2 new gasket but could this be the cause of the codes? I mean should I get under there and try and tighten the flanges up??

**02silverbird** · 10-22-2010, 08:21 PM

I don't think it's a bad 02 sensor because I did change the down flow sensor not even a month ago. Also I changed the fuel filter out about a year ago so I don't believe it is that. I did however take the screen off the MAF but before I changed out the PCV valve the car ran fine with the screen off. I did recently have the oil pan replaced due to the fact it was rusting out. When it was replaced one of the things that the shop did was lower my exhaust to get the oil pan out. They did however put in 2 new gaskets. So I'm not sure where to start first. Should I try cleaning the MAF sensor and see what happens?

**02silverbird** · 10-22-2010, 10:48 PM

anyone?

**02silverbird** · 10-22-2010, 10:56 PM

Would anyone know where I could get a new one from? Any web site would be a HUGE help!

Thanks everyone

**RyanJM** · 10-22-2010, 11:12 PM

Can try gmpartsdirect. Try a dealer to see if you can buy the part with the screen if so get the part # then order online and save the money. That's what I did when I needed new.speakers, a/s vent, and a headlights switch. Saved a lot there are several places to get oem parts online just good the part #'s. I know the speakers were half the dealer price even with my shop discount.

**02silverbird** · 10-22-2010, 11:17 PM

Do I really need it in a 2002 3.8? The reason I ask is because I'm getting codes that my car is running too lean. And I'm wondering if this may be the reason why.

**RyanJM** · 10-22-2010, 11:22 PM

Try some maf cleaner 1st to see if that helps. May just be dirty. I run a granatelli with no screen and have no problems on my ls1.

**02silverbird** · 10-22-2010, 11:24 PM

Thanks Ryan I hope that's all it is man..... I really have no clue where I could find a new screen from... The junk yards around here have no f bodys at all...

**LS3torque** · 10-23-2010, 04:12 AM

Originally Posted by 02silverbird

Thanks Ryan I hope that's all it is man..... I really have no clue where I could find a new screen from... The junk yards around here have no f bodys at all...

I dont think you need an "f body" maf to take a screen from, you should be able to rob one from any maf thats the same diameter. I know all about the Michigan junkyard f body thing too, if one does end up there its soo rare the parts are over priced accordingly. Good luck.

**TokerM** · 10-23-2010, 06:02 AM

I was going to say that it would be pretty odd for it to be O2 sensors. Since you're getting codes on both banks, what are the odds that BOTH O2s went out around the same time?

Oil pan doesn't even remotely seem connected.

Can you hear any kind of "air sucking or blowing" sound around the engine?

**98TransAmWs-6** · 10-23-2010, 08:10 AM

I doubt the lean condition is your maf screen. The maf screen is used to straighten the airflow. It could be that the maf is dirty though but more than likely you probably have a vacuum leak some where. For example the hose that goes behind the intake manifold. Not saying it is definately it but I would imagine that is it and would be a good place to look.

**02silverbird** · 10-23-2010, 08:54 AM

No I can't hear any air or anything car seems to run normal. The reason I said that I think it may be because of the oil pan i because the shop had to undo the exhaust from the manifolds to get the oil pan out. But they did however put new gaskets in and all. So I mean if they didn't tighten them down maybe air could be "sucking" through there.