A few months back I smelt petrol at the back of my car, so assumed it was running rich and purchased a new Lambda sensor.
After that my fuel economy slowly went downhill (went from 24ish to 16ish with gentle town driving) and I got it on Alfadiag and discovered a Lambda sensor not connected warning and when running the Lambda sensor graph was almost completely flat.
It turned out that the Lambda sensor wasn't the cause of the fuel smell, it was the seal around the fuel pump had become perished so was leaking. I fixed this, and thought the new Lambda sensor was faulty so I put the old one back on (I had kept it).
The new sensor worked fine for a bit, but now I am getting the exact same problem as before, it is giving me a Lambda sensor disconnected warning and the reading from the sensor is flat (but the lambda heating graph shows a W pattern).
Have I just been unlucky with the two sensors or is there something causing them to fail? Any ideas?