I have seen some post about this code P3081 but want to give my symptoms and see what advice you have. I have to get this inspected ASAP. I checked the coolant and it is good. I was having a little trouble with my heat and not sure if that has anything to do with it. My heat will blow hot for a short period then cool off. IF I leave the heat on low it will stay warm. I bought a ECT sensor in case I need it but my Temp gauge is consistent in the middle and not going back and forth. This CEL has been on for about 2 months and sometimes it would go off, when it first came on I took gas cap off and put it back on & the CEL went off then after a maybe 100 miles it comes back on. I started putting Shell 93 in with some fuel additive the went off after a few more miles it comes back on. ANY ADVICE IS APPRECIATED any detail on replacing the ECT on a 2003 A4 1.8T?