I have a 2002 wrx with a catback exhaust and thats the only mod.

Nice car.

I have had the P0172 code on for a while now which means that I am running lean.

No it doesn't. PO172 means Bank 1 is rich. There is only 1 bank on Subarus, but that's how it's reported.

You are not running lean. A PO171 would indicate you're running lean. What's happening in your case is that the ECU is unable to reduce fuel delivery sufficiently while in closed loop. This triggers a rich condition warning.

I was wondering what I should do to trouble shoot this without having to take it to the dealer to spend lots of money, any steps or suggestions are greatly appreciated thanks guys.

Well, "luckily" enough (I use the term very loosely) you can treat a PO172 almost the same as a PO171 in terms of troubleshooting. First, make sure the recirculation hose on the stock BPV is connected and intact. Next clean your MAF and make sure it's connected correctly. Then check the intake, filter housing, inlet, and all vacuum lines for visible faults. My bet is the MAF, provided the BPV hose is working fine.

Search of how to clean a MAF here and also there are a number of threads for troubleshooting a PO171 that will apply to your efforts too.

 

Nice car. No it doesn't. PO172 means Bank 1 is rich. There is only 1 bank on Subarus, but that's how it's reported. You are not running lean. A PO171 would indicate you're running lean. What's happening in your case is that the ECU is unable to reduce fuel delivery sufficiently while in closed loop. This triggers a rich condition warning. Well, "luckily" enough (I use the term very loosely) you can treat a PO172 almost the same as a PO171 in terms of troubleshooting. First, make sure the recirculation hose on the stock BPV is connected and intact. Next clean your MAF and make sure it's connected correctly. Then check the intake, filter housing, inlet, and all vacuum lines for visible faults. My bet is the MAF, provided the BPV hose is working fine. Search of how to clean a MAF here and also there are a number of threads for troubleshooting a PO171 that will apply to your efforts too.

Just so everyone knows that all boxer engines have two banks 1 being the passenger side and 2 being the drivers side, only inline have one bank!

 

Thanks, I did happen to notice that my recirculation hose is missing and that my BOV is loud becuase of it, I will have to go to a dismantler next week to get the hose, I also replaced the MAF about 3 months ago so I know that isnt the problem because i had this same problem before I replaced it. I will definately get the hose and please any more suggestions are greatly appreciated!

 

Thanks, I did happen to notice that my recirculation hose is missing and that my BOV is loud becuase of it,

That's it. Yay, I win!

I'm assuming by "BOV" you mean the stock unit. Use the stock unit. Fit a hose ASAP, you have what is essentially a hole in your intake system right now. See if a local parts store might have a hose (rated for vacuum) that'll fit even for the time being until you get the factory piece.

 

Ok sounds good, could this also be causing my car to run like crap and bog down under low throttle and seem like its lacking power in all gears?? sorry im a noob to subarus

 

Oh and yes its a stock BOV

 

Yes, running rich can cause bogging. Fuel economy is also probably not the car's strong suit right now. I'm confident that once you replace the hose you'll see a dramatic improvement.

Incidentally, the previous owner may not have been as careful as possible if the hose is MIA. It might be worthwhile to give the car a thorough once-over. Perform all the steps for troubleshooting a PO171 anyway, since you've done the most annoying part (dealt with the MAF) and the rest can just be a close visual inspection. Also make sure the car is completely up to date on all factory required maintenance items. These are great cars, and with care they'll run well for a long time.

 

Yeah man I have been getting bad gas Mialege, another thing i forgot to tell you, When I examind the turbo inlet and noticed that the recirculation hose was missing, the person before my plugged the hole of the turbo inlet with some kind of PVC material I am not sure if this piece is competely keeping air in could this also be bad?

 

Yes. Search for a photo of a stock 2002 turbo engine bay. Make sure your car looks like that.

 

Sounds like the previous owner made himself a poor-mans VTA BOV.

 

P0171 prob

Hey fellas, as im reading your posts im noticing that i am currently having problems of the same nature. I got the CEL on along with a blinking cruise light. I had the ECU checked and the code P0171 was read, stating the system is too lean, Bank 1. I was told i need to replace an o2 sensor, does that sound accurate, or could it be somthing else? I recently installed a CAI but have had no probs. since recently. I am new to the Suby world and need some help...thanx

 

Remove the CAI, install the correct Subaru intake, reset the ECU, and see if the problem goes away. That's the simplest explanation. Post back if the problem does not go away after replacing the factory intake, making sure it's fitted and sealed properly, and resetting the ECU (cleaning the MAF would be a good idea, the CAI may have let junk into the track and fouled it up).

 

a catback exhaust and thats the only mod. I have had the P0172 code on for a while now

For the record, it doesn't seem like the exhaust would have anything at all to do with the code. So don't worry about that mod.

Yeah man I have been getting bad gas Mialege

Search for mileage or fuel economy on the forums before you get your hopes up about a major increase. "Bad" for a WRX is 12-15 city, and even that isn't unheard of if you have a lead foot.

I recently installed a CAI

To elaborate on the previous post advising you to remove the CAI, there is extensive discussion of why that (and BOVs) are really not a good idea. Dig through the forums for more.

 

So, SD, could the injectors be an issue with this code?

 

I've never had to go that far down the troubleshooting list; I'd expect the injectors to generate additional codes frankly but have no practical experience.

 

If you're having trouble with your P0171, check out the link in my signature.

And to the op, that's amazing that it was the BOV. People run aftermarket VTA BOV's and don't throw that code. Glad you got it fixed!