bac2h

codes came back today. Too Lean. Looked for anything obvious when I pulled the airbox out and nothing jumped out at me. Ross Tech has a very detailed writeup about the whole fuel to air ratio thing based on the code and it may in fact be the MAF on it's way out. I guess it is not unreasonable to expect on a six year old car but the whole coincidence factor is just a little much for me to accept. Thoughts anyone?

skankpile

I had that same error and replaced the fuel filter & MAF... and the car drove for a week fine.. then the lean code was back.

My indy mechanic unpluged the motronic (hard reset) and when it rebooted or whatever it reset itself and its been fine since.

bac2h

Anyone know how to do this hard reset and where is the Motronic?

MP4.2+6.0

Read Mr. Bally's (lack of) progress on that a few posts below when he ran into the ECU "chastity belt." On my W12 they are in plain sight under the cowl cover, but I have never fooled w/ them.

Instead, normally done via VAG COM as a throttle adaptation, which is pretty std. practice when the MAF is changed or acts up. Need to search archives (try throttle adaptation); I haven't done it on a D3.

bac2h

hmmm...throttle adaptation he says, I will search...unless someone has the linky..

skankpile

I did the MAF adaptation as well (about 10 times), but that was for another code and the lean always came back along with my G188/P1171 angle sensor T.Body sensor fault.

On the D3 the throttle body adjustment is no different (but I wonder if on your W12 if you see an extra box since you have 2 MP4):
http://www.ross-tech.com/vag-com/cars/throttlebody.html

You may as well plug in and check the MAF block 003 and see what you are peaking to see if your MAF has gone ****-up.

From the Bently the lean was either the T.Body, fuel regulator, fuel pump, or MAF if memory serves... since I replaced all but the regulator and fuel pump I was at a loss, and strangely it only happened after the engine had warmed.

I'll disconnect a maf, T.Body and whatever, but I'm leery about touching the ~$3000 motronic so I'd leave that up to a tech you trust. I dont know how the tech new to do the hard-reset thing, but I guess thats why he's worth $100hr.

bac2h

<lol>..just searched and I asked about this back in October..oops my bad!!

awdinut

I had the code for lean on both banks. Bought a MAF and changed that because it was a cheap place to start. Code came back the next day and lter in the day one of the fuel pumps failed. So, you may be on borrowed time fuel pump wise...fortunately mine failed as I was in the repair shop parking lot. I still have a perfectly good MAF I'll sell for $20 if that does turn out to be the culprit.

MP4.2+6.0

Because of that dual synched box set up, hard to tune the box(es) at all either, like Lemiwinks allows w/ the 4.2 ECU (at least back on my C5). Both are in plain sight under the cowl cover over on the passenger side.

Other obvious reason for lean codes of course is vacuum leak, or really any leak downstream of the MAF.

bac2h

20 bucks for a MAF?? Where are you located? Love to switch one out and see if it helps..