CEL on (Linear Oxygen (Lambda) Sensor B2 S1)
 

My Check Engine Light (CEL) came on today, below error shown in VagCom. Cleared it and will see how long it takes to come back, but appears to be the O2 Sensor for Bank 2, Sensor 1.

I'm assuming that's the upstream sensor (Sensor 1), but is Bank 2 the passenger or driver side?

How difficult to replace for those that have done it? And what is the 'recommended' brand (Walker, Denso, Genuine Audi only, etc) to use?

Probably not a bad idea for me to order one up and get a jump on replacing it I'm guessing. But any other input from folks out there given the below diagnostic info?


-------------------------------------------------------------------------
1 Fault Found
19061 - Linear Oxygen (Lambda) Sensor B2 S1 Pump Current Trim Circuit: Open
P2629 - 004 - No Signal/Communication - MIL ON
Freeze Frame:
Fault Status: 11100100
Fault Priority: 0
Fault Frequency: 1
Mileage: 124475 km
Time Indication: 0

Freeze Frame:
RPM: 1812 /min
Load: 15.3 %
Speed: 45.0 km/h
Temperature: 87.0°C
Temperature: 32.0°C
Absolute Pres.: 0.0 mbar
Voltage: 14.097 V

That may be a problem to change Oxygen sensor. I do not think anyone did it here himself\herself. Bently recommends to pull engine off... Could it be done without it – that is a big question? So, before you'll order anything - try to research on it.
And if I remember correctly Bank 1 is the Passenger side, Bank 2 is Driver side of the engine. The first sensor would be the one on top, before Catalytic Converter.

Good luck!

Ho. Ly. Crap. Let's hope it doesn't boil down to an "engine removal" for a stupid O2 sensor. I'll drop the damn exhaust before doing that!

Any other input/advise if welcome...keep it coming. Especially if you have any "better" news :).

Johnny A6Q did on his W12 without removing the engine. Look for the post not too long ago. He did the whole tune up thing.
Darn, mine is just passed 82k miles... NOT looking forward on working on my car. I'm too lazy now. I'm still in honeymoon mode.

Cheers,

Louis

Looks like his was the temp sensor, not O2:
https://www.audiworld.com/forums/sho....php?t=2852419

But still looks like he had to pull some top-end of the motor. I'm holding out for someone that has an acceptable plan for O2 sensor replacement :).

Replace? Huh?
 

Isn't the code just suggesting it has a wiring problem? ...no signal... Before racing to replace any tough to do job even if it goes well, review the code again and track down the sensor. Then trace the wire back. If it's a W12, the main wiring join for all of them is by the (U.S.) passenger side air box. A ton of connectors there, including some buried underneath the more visible ones in the upper set/block.

From experience, the attachments for the connector brackets to the W12 air box are super fragile and are likely already broken at least in part. Don't be surprised to find some tie straps there, or resort to something yourself. Each time my car needed factory plug changes at the intervals (I had old Audi Care extended that went to 75K miles), the dealer "bought" me a new upper air box since they couldn't do it carefully enough. Plus, as I found later when I got a brief code, they broke an O2 connector lock at that air box join area. And fortunately it was just that. It was the "car" side at the harness connector, so I just ordered the connector housing as a bit part (there are a few types and you will notice the color coding there) and changed out. All good immediately, and none of the O2 replace nightmares people worry w/ W12's. Heck even my C5 4.2 I found myself literally stooped on top of the motor and squeezed under the open hood doing a blind reach a foot deep to get one of those 02's mounted tight in.

Net, review the code and then your relevant connector and wiring before rushing to get parts or suffering preemptive nightmares.

Ok, cleared the code...it came back immediately after 10miles/a few starts.

FYI mine is the 4.2L V8.

Anyone know where the O2 sensors terminate under the hood? Someone said by the air box, any chance it's this junction shown below? I don't want to start pulling stuff apart checking connectors until I'm positive I'm in the right spot:

You need a 4.2 wrencher to weigh in here (OP confirmed its a 4.2 not W12), but...
 

yes the colored connectors in your second picture look like O2 ones to me. On both my 2000 A6 4.2 and my A8 W12, and for that matter even on my old 96 2.8 A6 of yore, they are placed in groups and tend to have some color coding to the connector plastic housings (brown, black, green, etc.).

Get a 4.2 owner to tell you where they are, and tie off the specific one at issue location-wise to that code you have by bank so you can trace it from the general sensor area back to the connector.

Make sure you know how to open them in general--it's that standard bigger multiwire connector with the locking tab Audi uses a lot, both for stuff like this and as a not too different flavor on the plug coil packs (at least of my C5 vintage). In particular don't pry hard w/ a screwdriver at the tab--though with experience you will have a feel for it and may well use a screwdriver in part. Often the trick is applying a bit of pressure to push the connector TOGETHER as you trigger the locking tab and then simultaneously start to pull the connector apart. The usual mistakes are either breaking the locking tab or yanking at individual conductors and having them tear out of the connectors. Avoid those two things and mostly its just a question of time and finesse before the locking tab releases and it slides right apart. Meanwhile, a guess is you may well find an already broken locking tab or a disengaged/pulled conductor at the connector block is driving your code issue. If you are lucky, someone just didn't re-lock the offending connector in full or it simply needs to be unplugged and then plugged back in to break thru a bit of surface corrosion and electrical resistance.

Just a quick update, the 1st time I just "cleared" the codes they came back within 10 miles or a few starts (as previously described).

After MP4.2+6.0 confirming the connectors I posted pics of were the O2s, I took off the bracket and unplugged/plugged everything back in. The connectors themselves were spotless - not an ounce of corrosion, and did not seem loose/etc.

However, after I did this and cleared the codes I've been 100+ miles without CEL coming on. We'll see, I'm sort of "expecting" it to pop back on but so far so good. I visually traced the wire from the upstream driverside O2 (you can see it from the engine bay) and the wire looked intact/ok, so not sure why it would have the error of 'no power' showing up.

I'm also optimistic with the right tools I could probably get to this particular O2 from the top/engine compartment if really push came to shove. But I'm hoping it doesn't come to that and stays off :).

Did you ever find a solution?