I ordered the Bank 3 Sensor 1 replacement just now [07P906265H G285] and I'll have a go at replacing it myself. I checked this morning and this fault was reported 7 times since I reset the all the DTC's on Tuesday. So I'm pretty sure it needs changed out.
(Weirdly, I reset the DTC's on Tuesday ahead of a 240 mile drive and the car behaved impeccably; no warning lights, no "
ACC and Audi Braking Guard not available" message, nothing, for the full journey!).
I found the connectors, they're really easy to reach, they're at the back of the engine, in the centre, under the windscreen. B3S1 sensor plug is the grey one, 7th from the left. Please see photos below.
1) The connectors look like they have a tab which pulls up to release them...?
2) The routing of the wire looks like a nightmare. The wires seem to be fabric wrapped and then disappear into some kind of large tapered rubber grommet.
