Help, I'm trying to diagnose whats wrong here. Ive plugged in the VCDS and here is the screen shot of the fault codes and a pic of the O2 sensor. I've tested for a supply to the heater and a supply to the sensor and these are fine. Also the resistance of the heater seems ok. There is a grey/brown deposit on the sensor, but its not thick and Im not sure whether this could affect its operation.   Do I just replace the sensor? or could it be something else?