W12 Lambda sensor Replacement Guide

[daviesbike]

Well my Bank 1 sensor 1 on the W12 failed and caused the cell to come on emmissions below threshold ect so i changed the sensor and it took me all of about 10 mins to do so hears how i did it.


first off remove the maf sensor followed by the air box it should look like this by now ...




Next i used a pair of plumbers grips to loosen off the sensor .. then unclip it and remove .. like this





and then the new sensor





now reverse the procedure ... and bingo .. no more cell light and better mpg again

hope its help full to people who are scared of tackeling the W12 themselves .... its not such a scary beast

[Architex_mA8tey]

Added to repair sticky

[A8 Doc]

Blimey that was far too easy.... Sure the A8 4.2 is harder than that!

How's the codes now Guy?

[carterleeds]

can i do this for my 4.2 v8 d3?

[GlynH]

Interesting discovery & solution db

I had heard it could be as much as £3k to change a Lambda probe on a W12 (depending upon which one it was that had failed) as it was an engine out job...scary indeed!

Can I ask how you identified which of the 8 probes(!) it was that had failed and what fault code was reported by VCDS?

Thanks & kind regards,
-=Glyn=-

[daviesbike]

well it was plugged into vag com and it stated bank 1 sensor 1 . but you can actually get to all 4 under the bonnet of course you have to take the air boxes out ect and to get at the rear ones its a bit tight but if you take the intake manifold off you can get at them both fairly easy.. engine out would be 4 new cats as you cant take the manifold off without the engine out i guess. but lambdas easy peezy

P2251

P0135

thats the codes i had

[Horrgakx]

I need to change one on mine too (6.3 W12 D4), bank 1 sensor 1. I belive it to be the one on the far right side and looks pretty similar in terms of access to this of yours.

Csn I ask what you did with the wire though? The sensor looks like it comes complete with wire and plug at the other end. I think it goes into a bank of plugs somewhere under the right side airbox...?

[steamship]

Originally Posted by Horrgakx

Csn I ask what you did with the wire though? The sensor looks like it comes complete with wire and plug at the other end. I think it goes into a bank of plugs somewhere under the right side airbox...?

The OP can't respond as they were banned several years ago. The O2 sensor does indeed come with a plug on the end. In terms of the question you asked, and location, I've already detailed this in your other thread:

https://forum.a8parts.co.uk/showpost...19&postcount=6

If you use the PDF as instructed, it also shows where the individual sensor wires go to, and their route. Even without that, all you have to do is lay out the new one along the same route before removing it at either end.

[Horrgakx]

Thanks for your reply, I didn't realise he'd gone :/

I'd seen this thread by chance and jumped on it hoping there would be some photos of the onward journey of the cable. I appreciate the PDF but it's always nice to have photos
Also, he said it's bank 1 sensor 1, which is the same as mine, but his appears to be on the very opposite side of the engine to mine... the photos above are on the left side (UK off-side) but my sensor (bank 1 sensor 1), I believe, is on the right side (UK near-side).

I've got an air filter on order right now (I actually bought one a couple of weeks ago thinking they were supplied in a pair due to the photos on LLParts and the price of them but I had to order another when just a single one arrived), so on a sunny weekend, I intend to change them and take that opportunity to have a look at accessing the Lambda sensor (and the plug-end) when I do that job.

(Oh, and I've corrected the location of the sensor, which is bank 1 sensor 1.)