MP4.2+6.0

1. Given the poking around w/ the PCV valve and dealer thinking the same, look at what Audi officially calls the "suction jet pump." Why in the world they call it that, who knows--it's just a Y shaped sort of hose connector with a ball in it that seems to act like a check valve. Frankly, it is constructed more like a typical (cheap) PCV valve than Audi's ultimate Rube Goldberg overpriced and designed one. Part is also known in the vernacular as the suck pump or suck valve. See part 25 of this diagram: Audi - A8Q - 2006 - Engine, Clutch Teile Katalog (Pats Catalog)

You will see it sits right off the intake big rubber boot/duct, so of course if there is any leak at either the physical connection or something wrong with it internally that might lead to a fix. Honestly, I have never been clear on what it even does functionally, but my C5 2000 4.2 had one and so does the W12. It is in the vacuum side of things--hence the "suck" or "suction" terminology. It does have a ball type one way flow thing built into it from changing it on my C5--like a PCV valve does. It was associated w/ oil burning issues for some reason on C5 A6's, particularly 2.7Ts. In any case, not a very expensive part (a lot less than the PCV valve)--$50 to $60 dealer OE, as little as about $20 aftermarket.

2. Yes, look at fuel pressure.

3. Consider vacuum leaks at the injector seals. But, I would expect it to show more on one cylinder head side than the other--wherever the leak is. Yet your O2 codes said both sides.

4. Recheck codes BTW. Are they still clearly on both sides? Does one side come up more consistently than the other?

5. But for fact code is on both sides (but see #4--check again), given other things you have checked already, I would start to question whether the "data" is reliable. As in, is the issue with the O2 sensor itself? But again, codes on both sides tend to argue against some weird failure of both sides' sensors at the same time.

nathanwind

Quick update...and I'm being cautiously optimistic here. Previously, without fail I'd clear the codes and within 1-2 ignition cycles and 5-10 miles both CEL/MIL would come on for B1 & B2 (as described above).

However, the last time I cleared the codes was about 120 miles (85350mi) / 2-weeks ago. I added a can of BG44K to a full tank of gas at that time, cleared all codes and haven't really looked at it since then.

Fast forward, this morning I was at 85469mi...and when I went and pulled the codes today, only ONE side was on [B2 S1: Signal too Low (Lean) P2197]. This is a departure from the "both" sides/codes scenario that has been pretty consistent (12+ times or so during all prior testing).

I cleared the code, did a test-drive to about 85483 which included 6 or so ignition cycles - so far NO CODES back on. I wanted to wait until I was down to about 1/2 tank of gas so the BG44K could "do its thing" before even coming back to review/test. Again, I'm being cautiously optimistic, and the true test will be more test drives to get more than just 15 or so miles on it. But I'm liking what I see so far!

nathanwind

Another update, I finally put some real miles on the car last week - had a 500 mile road trip (one way). On the way up, was monitoring/checking codes periodically. The P2197 lean code went away....BUT was replaced (during the trip) two or three times by:

19061 - Linear Oxygen (Lambda) Sensor B2 S1 Pump Current Trim Circuit: Open
P2629 - 004 - No Signal/Communication - MIL ON

However, I cleared these codes during the trip...and so far they have NOT come back (I'm at around 86,000 miles now). The good news is I have another 425-miles or so to drive back in the morning, so this will be another good follow-up test to see if any codes pop back up. Part of me wonders now if I just had a crap tank of gas that caused all of these issues? Or maybe just the injectors got clogged up slightly because of it, and the BG44K did the trick? May be a little optimistic, but I guess the test drive tomorrow will give a little more info...

nathanwind

Finished the return trip, mileage at 86600....and clean as a whistle! No CEL/MIL at all, did a scan and everything looks great.

I'm not a big "additive" guy, but it looks like that BG44K did the trick. I've got to assume that it was an injector or injectors clogged or slightly clogged causing the lean codes. If so, not bad for a $25 fix!

As a real litmus test, I'd like to see SilverA8oh maybe do the same thing with a BG44K treatment on his and see if it also clears his dual lean codes.

Alexxelax

012850 - Oxygen (Lambda) Sensor B4 S1; Heating Circuit
P3232 - 004 - Open - MIL ON
Freeze Frame:
Fault Status: 11100100
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 160647 km
Time Indication: 0
Date: 2015.03.13
Time: 17:34:30

Freeze Frame:
RPM: 641 /min
Load: 22.7 %
Speed: 0.0 km/h
Temperature: 104.0°C
Temperature: 54.0°C
Absolute Pres.: 1030.0 mbar
Voltage: 13.208 V

were is the B4S1 located ?

Mister Bally

The service manual will spell it out for you since it depends on your engine code. It is basically mandatory to have one for your vehicle to work on it. Sometimes the Ross-Tech wiki will have basic information. The service manual describes the procedure to R&R the sensor itself.

Read & heed: https://www.audiworld.com/forums/a8-...-read-2877219/

Alexxelax

I have looked at the Elsawin, ETKA, and googled, but nothing that shows me the location of B4S1. I know its sensor one, but B=Bank 4?

mishar

Which engine we are talking about?

Alexxelax

It is a S8 5.2 v10 BSM

mishar

Not sure but it looks like one at the entrance to the front left catalytic converter.