nathanwind

Checked fuse #6 (lamba sensor) for kicks, but all tested fine...

So after a few more talks last evening with a relative that is in the auto repair industry, sort of leaning even more towards the MAF as a very likely culprit as well. Certainly this is still all a shot in the dark at the moment, and plan to still do some additional trouble shooting for vacuum leaks and pull the FPR vacuum line to test/inspect the diaphragm.

Barring any faults being discovered above, it looks like PartsGeek has a Bosch MAF (and appears to be new, and not reman'd from what I can tell) for like $115 shipped:
0280218069 | Partsgeek.com

Should I be looking elsewhere at an alternate/reputable source for these? I've ordered some other non-Audi parts from PartsGeek with success before, so seems like a decent choice/option and the price is certainly right - but if there's a better vendor for "Audi-specific" parts I should consider I'm all ears.

It was $230 at the local Audi dealer parts dept, so figured for 1/2 the price I'd just order it online.

SilverA8oh

I have had the same issue and still diagnosing. Here's what I have done:

Replaced broken plastic short arms connecting manifold intake diaphragm pods (use Billet)
Replaced both air intake diaphragm pods (cracked)
Replaced manifold gaskets
Tested MAF was ok but replaced it anyway with miles at 150k (tested airflow at high speed and pre-airflow was fine)
Replaced fuel filter
Tightened vac hose connector that was loose behind manifold when replacing gaskets
Used Seafoam to purge carbon through manifold when idling

Each time cleared codes and drove it. Regular cycles then CEL friend came back on. The car runs just fine.

I have not checked the fuse as Mishar mentioned and have not replaced the PVC valve. This has been a headache for sure.

Any other ideas would be appreciated!

Cheers

nathanwind

Misery loves company! So are you seeing the exact same P2195/2197 codes as I posted? Is it throwing any "other" codes as well? Or just the 2195/2197?

nathanwind

Quick update. First (though admittedly I sort of *knew* this would not be the issue I was seeing as originally described) I was looking for any possible air/vacuum leaks. So i was spraying a little carb/choke cleaner around the usual suspect areas (essentially if there is any vacuum leaks, it will suck in the carb cleaner and cause it to slightly choke out at idle...which is a telltale sign). Anyhow, around the area of the PCV Valve / Crankcase Breather I got a little overspray on it and it sucked it in...and immediately gave what I will describe as a little "horn" sound (like a bad sax player or something). Long story short, months ago I was having an issue with that sound happening at times when I'd pull back into the house or parking spot and shut it down (then the long drawn out "horn" sound would happen as the car was shutting down). Anyhow, that said it suddenly dawned on me that perhaps that PCV valve was clogging just slightly (which is what happened when I sprayed a little carb cleaner over there, it essentially closed down the outlet of the PCV valve and caused the same sound/issue I had heard months prior). So...it was an excuse to change out a part I finally identified as a prior issue (even though that issue had since gone away). I knew this was nothing in theory to do with the above codes, but figured it was worth a shot.

Cleared the codes, gave it a test drive, and while I did make it about 15-miles or so (which is more than the prior 5-6) the CEL did come back in (in other words the PCV valve was not the issue, which is no surprise).

However, the strange thing was this time on B2 S1 instead of getting the "lean" code...I got a "Pump Current Trim Circuit: Open" error (codes below). The B1 S1 still threw the same P2195 lean code as previously - but I find it a bit odd that B2 S1 is now showing a P2629 circuit error in lieu of the P2197 it has thrown prior.

Could this mean that the O2 sensors are really the culprit in this situation? Or should I just clear once again and see what comes back next time, chalking this up to a possible fluke?

-------------------------------------------------------------------------------
Address 01: Engine Labels: None
Part No SW: 4E0 910 560 P HW: 4E0 907 560
Component: 4.2L V8/5V G 0010
Revision: --H01--- Serial number: AUX3Z0E9776339
Coding: 0007773
Shop #: WSC 02313 785 00200

2 Faults Found
19061 - Linear Oxygen (Lambda) Sensor B2 S1 Pump Current Trim Circuit: Open
P2629 - 004 - No Signal/Communication
Freeze Frame:
Fault Status: 01100100
Fault Priority: 0
Fault Frequency: 2
Mileage: 137244 km
Time Indication: 0

Freeze Frame:
RPM: 1964 /min
Load: 15.3 %
Speed: 66.0 km/h
Temperature: 92.0°C
Temperature: 21.0°C
Absolute Pres.: 0.0 mbar
Voltage: 14.478 V

18627 - Oxygen (Lambda) Sensor B1 S1: Signal too Low (Lean)
P2195 - 008 - Implausible Signal - MIL ON
Freeze Frame:
Fault Status: 11101000
Fault Priority: 0
Fault Frequency: 1
Mileage: 137253 km
Time Indication: 0

Freeze Frame:
RPM: 2000 /min
Load: 48.6 %
Speed: 71.0 km/h
Temperature: 91.0°C
Temperature: 18.0°C
Absolute Pres.: 0.0 mbar
Voltage: 14.224 V

Readiness: 0100 1101

-------------------------------------------------------------------------------

mishar

I would clear those codes and test again.

MP4.2+6.0

As Misha says, first clear codes/gather more data. Since it says OPEN circuit, it could be a bad O2 sensor, but it could also be the connector where the sensor plugs into the wiring harness. That's a definite issue with W12's through at least 2006, and there is a TSB for it for that motor. The poor man's fix is just unplug the connector and try some Deoxit. In my case, I eventually concluded a conductor right near one of the terminals to the connector (on the car harness side) was bad--similar to what the TSB gets at when it talks about some issues with the crimping IIRC. So I bought the pre-made conductors with the pins precisely crimped on, and a new connector end. Fixed issue definitively, which previously was a CEL and code every 300 to 1,000 miles more or less.

Info was here, as well as elsewhere around that thread for context: Oxygen sensor, codes p0150,p0155,p2254 - Page 2 - AudiWorld Forums

nathanwind

So this is actually very interesting. Mainly, because about a year and a half ago I was having an issue with the "Pump Circuit Open" on one of the sensors:
https://www.audiworld.com/forums/a8-...b2-s1-2854338/

Because it was so long ago, I never really connected in my mind that they may be related. But now that I read your above post (and the other thread), it now dawns on me that to solve my original issue unplugging, cleaning with some electrical contact cleaner, and reassembling seemed to solve the problem. That said....I suppose it's certainly feasible that the factory plugs/connectors *could* be the culprit if they've deteriorated even further. In this process for the recent issue I did take them apart to inspect early on, but all looked fine (but maybe "looks" can be deceiving).

You're referring to these connectors below that you had an issue with on your W12, is that correct? Where did you purchase the new plastic connectors from in the black/brown? Did you get those from Audiusaparts.com as well? Can you not reuse the old plastic connectors, but with just the new wires?

MP4.2+6.0

Yes, you get the connectors from audiusaparts.com. Where I get all mine (Romney). You can often find part numbers on them if you look really carefully or blow up a picture of them on a phone. Or, if I describe its color, function and what it connects to, Romney usually either knows it, or if a little unsure/unclear sends me a screen shot of the parts diagram o I can see where the one is he thinks is correct. Big picture, if you look long enough, virtually every connector you find on an Audi wiring harness you can now buy as piece parts; you don't have to put up with bad connectors or broken locking tabs.

For O2 connectors, there are brown ones and black ones; the color distinguishes which bank but are otherwise identical if they are the sensors before the cats. The pre-cat ones are six pin, while the post cat ones are fewer pins and a little different shape.

In theory you can reuse the connector, but i virtually absolutely never would. The terminals are extremely hard to remove from the connectors and often get damaged somewhat doing so. Sometimes they just seem to not want to come out at all. There are special tools to assist, but I don't think they make it either foolproof or simple. Also in practice the old connector plastic gets heat soaked and brittle, os the locking tabs often break. Broken locking tabs on an O2 sensor, or most any motor sensor, MAF, spark plug coil, etc. are not good.

If anything I use the brittleness to my advantage. Since the end individual wire terminals are so hard to get out undamaged by individually trying to extract them, I basically just start shattering the connector intentionally by squeezing it in places with basic pliers where I can see I won't bend one of the wire end terminals. I've tried cutting them with a utility knife--which sometimes you have to if the plastic hasn't gotten heat soaked and hardened--but the plastic shattering method is way faster and less risky to both car and my hands. I've probably done it a dozen times now, and can do it in about 5 minutes with no damage to the conductor end terminals.

As far as the wires and possible issues there, as you noted they can look just fine. Mine did. But, per the TSB there can be slight issues where the wire strands are crimped to the terminal at the end and have to make a solid connection with very little incremental resistance. You have no way of seeing that with the terminals stuck into the connector plastic. Also, if you look at the wires themselves at these O2 connectors, two are much thicker than the others. Those two are for the heating function for modern 02's. I don't worry about those two breaking. But the others are actually a pretty fine wire, and I can see just with jostling the connectors w routine service and maybe some repairs how internally the wire strands may either get pulled off of the terminal end partially, or can basically break internally, particularly right at the head of the connector where the factory harness emerges. That area no doubt get flexed and jostled by maintenance and repair work over time.

Net net, mine looked good. I did all the Deoxit stuff, visual inspections, etc. In the end it was somewhere in the wiring close to that connector. I expect it was either the crimping on the end terminals that fit in the connector, or that one of the wires was broken or frayed internally in the first inch or so right near the connector plastic itself.

SilverA8oh

Same two codes. I even ordered a replacement gas cap from Audi to check if that was an issue. Interestingly the replacement cap for the 04 D3 throws the red gas cap open light on the dashboard. Audi parts couldn't figure out why so they credited my card and I was on my way.

This week I may replace the PCV valve. Slowly narrowing this down is a pain.

Cheers

nathanwind

Keep in mind though, like I said a new PCV Valve did NOT do anything for mine. Between the two of us (and the other kind folks here on the board) we'll figure it out!

Also, small interesting development. I was playing around today with the car doing some more troubleshooting - had it running with the hood open, and realized when I "blip" the throttle I get a tiny bit of a "sucking air" sound briefly. I really don't recall this being their prior, though I suppose it could have been. It is harder to hear with the hood closed, but is definitely still there. The only thing I've changed is the PCV Valve / Crankcase Breather at the top of the motor (and yes, I made certain that all clamps were snug on this). Maybe this is normal function for the PCV Valve since it is a breather of sorts? And an indicator that my other one may have been a bit stuffed up?

That said - is this normal? OR....could this be the vacuum leak and/or cause of my issue?