ironworker

I have a 2010 a4 and the check engine light came on after I passed a car on the highway. I checked the computer and the error code was p2099 error turbo underboost. I took the turbo diverted valve out and it’s a solenoid valve not the old plunger type. I put old diverted valve back in and reset the computer and the engine light came back on again. It’s been two weeks now and the engine light went out. Not sure if it’s the diverter valve or a wastegate problem does anyone have any suggestions.

kike805

I think you are gonna need a new turbo pretty soon. The wastegate go bad on those turbos really fast,I have never seen a sensor go bad, most of the time is the wastegate, unless you install a special clip to keep the wastegate in place..

to8’place.

DeamonMachine

Is the error code P0299 vs p2099? That could be a turbo recirc valve (N249) or the turbo itself. I'm sure there's a few procedures you could find to test out the various pieces.

whwood3

Mine threw that code intermittently (a couple times a year, usually accompanying large throttle application under low rpm/high load) It was the diverter valve on mine. The other cause as I understand it is a worn wastegate bushing that you can check with a borescope through the upstream oxygen sensor hole (looking for wastegate seating tension) or by assessing the playing the wastegate pivot shaft. That would generally leak all the time, the part throttle to full throttle transition is typically the diverter valve not transitioning from recirc mode when the throttle opens.