Hello all, hoping you can help diagnose this:

2009 A3 2.0T. 120K miles.

Last week noticed the car had an oil leak, appeared to be coming from area between engine and trans. Almost simultaneously it threw a couple of codes - P2279 and P0171. Did my research and guessed it was the PCV failing, which lead to the rear main seal blowing out. Removed the PCV and the button valve underneath the part was very suspect - shrunken, valve felt like it was dried out and likely not sealing. Replaced the part with a new OEM unit and cleared the code, made an appointment with the shop to replace the seal.

Note also that the car is running fine, no indications which could lead to the codes, idles fine, accelerates, cruises fine. Visual inspection showed no old/leaking hoses. Some oil leaking from the base of PCV valve to valve cover but the gasket was old and compressed so was not unexpected. Looked like the original PCV valve (495 B)

Drove the car for a week, no problem. Now a couple of days before the rear seal appointment and I'm getting a P0171 code again (So far no P2279 code). No performance issues, idles fine. So I'm wondering how likely it is that the P0171 code is just a stored code come back to life - I cleared it initially with a simple scan tool, and all monitors (8) show clear. I guess I'm reluctant to get the seal fixed if the underlying issue of overpressurization of the crankcase isn't fixed yet.

 

That code is a "lean" code. You still have a small vacuum leak somewhere.

 

Hi, I have the same issue and the same two error codes on my A3. I was thinking a bad PCV valve because the diaphragm was broke. I bought a Dorman replecement part, changed the part but the two codes come back with weird idle but no misfire. Like you, I have an oil leak between my engine ans trans. But what's the link betwen the oil leak and the PCV valve? So you have changed the complete PCV block and all became to normal? Or you've repair the oil leak to?