2006A8LW12

Had intake off and did thermostat - just started seeing this code

Any thoughts ? Would a bad injector cause this ?

004225 - Mixture Regulation; Bank 3; Range 1
P1081 - 004 - Lean Limit Exceeded - Intermittent - MIL ON
Freeze Frame:
Fault Status: 10100100
Fault Priority: 0
Fault Frequency: 2
Reset counter: 255
Mileage: 177982 km
Time Indication: 0

Freeze Frame:
RPM: 817 /min
Load: 20.8 %
Speed: 20.0 km/h
Temperature: 106.0∞C
Temperature: 37.0∞C
Absolute Pres.: 990.0 mbar
Voltage: 12.954 V

005634 - Power Supply Terminal 30
P1602 - 002 - Voltage too Low - Intermittent
Freeze Frame:
Fault Status: 10100100
Fault Priority: 0
Fault Frequency: 2
Reset counter: 255
Mileage: 177982 km
Time Indication: 0

MP4.2+6.0

Lean = likely vacuum leak. Bank 3 puts it at the USA driver's side front in general.

Did you change the o rings on the injectors? And did you have to pull them to get fuel rail out and get to thermostat? s in, they got disturbed and may now be showing a little less tight fit.

There are apparently two designs where some need the rail out, but not others. I had to pull rail w/ injectors on mine. I didn't end up w/ a leak, but certainly can see how it can happen. Others with W12's have reported some injector seal issues, again maybe connected to other repair work like this.

If it were both banks, I wouldn't focus on the injectors but rather the various connections, clamps, hoses, etc. But yours is more isolated to only a portion of one side.

TSHong

+1, I had to replace my injector seals because they were leaking vacuum just enough to trigger a fault code after my tstat replacement.

2006A8LW12

Yes I had to pull the rails, I did replace the bottom injector seals on all of the injectors.
I didn't actually unplug the injectors from the electrical connection or remove them from the rail. I am wondering if some debris/dirt got under the seal and is causing a small leak ? this would cause a lean condition correct ?

MP4.2+6.0

Yes, any vacuum leak will cause a lean condition/code. Did any of the injector bodies break at all during removal--a piece cracking off? Ask me how I know... If so, another suspect. You could also use a rubber friendly seal/lubricant on the o rings. Stuff sold for swimming pool equipment seals or plumbing. Likewise FWIW, when I pulled mine I left the injectors connected to rail. I did unplug them all to remove the whole rail assembly fully.

You also replaced riser gaskets, correct? The upper one is cheap and I always replace, but now recalling I think the lower costs more. If not replaced, you would want to coat them lightly with a sealant. One other suggestion is simply recheck tightness the upper manifold Torx screws you can easily access under the motor trim cover, particularly checking driver's side toward front.

The.aviator2

You may want to check your PCV condition. I've recently missed up mine and got those lean condition faults + huge suction when opening oil cap. I corrected it and the faults cleared for good.

MP4.2+6.0

This is a good point too. For OP and specific to W12, look at those plastic flex hoses that you have to unfasten when removing the upper intake manifold to do the kind of work you did. The ones toward the middle of the motor that go to that black plastic box shaped thing are the fine oil separators that have the PCV equivalent function. There are also the ones in front of the motor on each side. You know the codes tell you to look critically at driver's side.

On mine, dealer broke one and then concealed the damage with duct tape applied under an insulating sleeve area--thanks Burlingame Audi/Rector Motors, Burlingame CA to name names. I found it the first time I ever pulled manifold post the warranty and AudiCare periods, and they had done all the service work since new. Two of the others (4 total) had at least partially broken end fittings. The plastic does get brittle with heat soak and oil vapor over the years.

Look at all of them critically. If cracked along the length, with quality electrical tape applied carefully (best if piece is out of the car) you can bandaid it for a while. If end fittings are messed up--which also have sort of an o ring seal built in too--they should be replaced in general. If you see signs of oil at the connectors or along length, they have an issue. Roll back any insulation type covering they have in certain areas to see if oil is underneath--where I found the hidden tape splice. They are pricy, and use a specific size and shape unique to W12. I bit bullet and replaced them with one of my intake pulls.

2006A8LW12

Yep - those 4 hoses are all new - they disintegrated when i pulled intake first time - heat soaked and brittle. I ordered new Throttle body gaskets, Intake box gasket (one on top of manifold) and am going to pull drivers side fuel rail and check o-rings for debris and all. Over the weekend should dive into it

MP4.2+6.0

FWIW, I pull intake complete with throttle bodies and also save buying those two gaskets that add more $. All you need to do incrementally is tip it upward to get the one hose undone under the passenger side throttle body that can't be reached otherwise. Likewise during re-assembly you need to connect that one hose again with intake tipped upward before lowering back down. Saves a bit of time in total job too.