View Full Version : Fuel trim indicating a leak

03-04-2017, 10:31 AM
So I am looking for a little guidance. I am trying to get my A4 to pass inspection and recently changed the solenoid on the CCT which seems to have gotten rid of that code, but the readiness wasn't coming up and then I got a CEL for P0171 which I thought was indicating a vacuum leak. Looking around I did find a crack in an elbow that I think comes up from the SAI to the valve at the back of the head. I made a temp fix of this just to look for other leaks. I think there is a hissing sound coming from the back right side of the head. Looking down that rubber T under the intake appears to be dry rotted so I am assuming that is the likely culprit. So my plan was to replace that elbow, the T, breather hose and PCV. But part of me thinks the noise is coming from the suction pump. Is this supposed to have a sound like this? Also, using Torque I can see when I first start it up the STFT is 0 but soon after the SAI pump shuts off it goes to like 25 but the entire time my vacuum is reporting +20mm Hg so now I am wondering if there really is a vac leak. Could this be a mass airflow issue or O2 sensors? Any suggestions on how to diagnose this?

03-04-2017, 11:19 AM
I was reading through a few other threads and Walky was suggesting this code is often the MAF, so I just pulled mine to give it a spray down and notice on one side there is a spot for a resistor but mine doesn't have one. WTF? It isn't inside the housing either. Do all model years have this?