I'm experiencing a problem with my car in which i keep throwing up a cel code P0172. My o2 sensor pre-cat was recently changed about 5 months ago and has been running perfectly fine. I had an aftermarket exhaust system which bolted on after the secondary o2 sensor all the way back for over a year now and everything was working fine. I recently removed the exhaust and replaced my stock exhaust back onto the vehicle and ever since i've been getting this vehicle code. All i did was remove 2 bolts took off the aftermarket exhaust then bolted back up the stock exhaust. I can barely drive 5 miles without it coming back on after i clear it. I checked all the possible causes and everything is good. no leaks anywhere. Car drives though as if nothings wrong so i'm totally confused as i've never encountered this issue before. Car has 41k miles on it. Injectors and sparks plugs are all stock. The only thing still aftermarket is my injen cold air intake which i had on longer than the exhaust and never encountered any problems or cel lights. If there's anything that i may have missed please let me know. Your help would be greatly appreciated as i am a week passed due for an inspection and i surely wont pass with this code on. Thanks

 

Um....yea I don't think you did your research on this particular OBDII code.

Here you go. http://www.obd-codes.com/p0172

 

Umm thanks but i'm well aware of this code and what it means. As i mentioned previously i've been driving for over a year on my original setup but literally the minute i put the stock exhaust back on i started up the car and drove no more than 2 miles then the light came on.

But thanks anyway i'm sure someone else can give me a little better idea to what might be wrong other than stating the obvious.

 

well...i think you should start by tackling the possible sources for faults with this code, like the MAF sensor, it says it can be dirtied by oiled air filters, and you have an INJEN air filter on your car. so i'd start with cleaning the MAF sensor. reset the ECU, see if it comes back.

i know you said you only did some exhaust swapping and such lately, but the timing could just be a coincidence.

 

LOL Wow!! Do you know how to read?? LOL!


Clean your MAF sensor with contact and circuit cleaner and reset ecu or remove code with obdII scanner. If you don't have any Vacuum leaks and the code comes on again, you probably need a new MAF sensor. I would also toss that Injen filter and get a dry flow filter from AEM.

 

My bad if i came at you the wrong way. I've been having nothing but bad luck with this car and its starting to get to me.

I will check the MAF sensor and see if its dirty. Can i clean the MAF sensor with brake cleaner or carb cleaner? Also i changed my intake filter 4 months ago to a spectre brand from autozone.

One more thing not sure if thsi could've caused it but right after i put back the stock exhaust and started the car i 2 stepped it for a bit just to hear how it would sound with the stock exhaust. It triggered the usual misfire CEL but i cleared it as i always do and everything goes back to normal. Could i have fouled out the spark plugs or sensor?

 

spectre FTL

I guess you wouldn't know unless you actually checked the plugs

 

NO worries man. I had the same exact cel on my B a month ago.

I dunno if you can use break cleaner so I would just buy contact and circuit cleaner to be on the safe side. Its cheap anyways. From what that website says about the CEL, it has nothing to do with spark plugs.

And the reason why I say, get an AEM dry flow filter is because it does not have any oil in it so your MAF won't get dirty. Most other aftermarket air filters that are sold do have oil in them which can damage the MAF sensor.

Just clean out your MAF sensor and plug for it, let them dry, get an AEM dry flow and toss that crappy filter, and clear the code. Hopefully it won't come back.