bharrington

Hey all,

I have been dealing with the stubborn P2187 and 04105 CEL codes on my wife's A4 and cannot seem to find the issue. I have replaced the PCV valve twice with OEM parts from Audi, the N80 valve has been replaced, and the CEL keeps coming on. Anyone have any experience with this issue and found a problem that was not the PCV or N80? the car has 120K miles on it.

SMac770

Is this a CAE (plastic IM) or CPM (metal IM) engine? On the CAE, you can easily isolate the PCV system as an air ingestion path by disconnecting the PCV hose from the IM and plugging the port on the IM. Can do it on the CPM too, but believe it's far more annoying to accomplish because of how that elbow is routed.

Lean, not enough fuel, too much oxygen at the lambda sensor before the cat. You could have an exhaust leak too, loose bolts on the turbo, etc. 120k miles, the LSU 4.9 lambda sensor does have the aging issue of the LSU 4.2 style (always replace them every 80-100k type concern), but maybe it's developing issues. How lean are you? What's your long term mix trim and long term idle trim? When the car is warmed up, what is your camshaft adaptation intake bank 1 value?

1stGOAT

Lean condition common causes air - air getting in after the MAF - that air would be unmetered and unaccounted for in the tune
Unmetered air entering system
Air getting in to turbo due to leak between MAF and turbo
Cracked or disconnected vacuum line
Dirty or bad air sensor - MAF


Of lacking fuel
Fuel injector plugged
HPFP failing
Fuel filter needs to be replaced

Or a failing O2 sensor - the trailing one after the catalytic converter - not reading the exhaust gases correctly

Good luck sir. There are diagnostic tools that can help eliminate the above issues as a cause. I use Ross-Tech.com VCDS cable and win software.