Audi condition: 01 MIL on, engine stalls or idles erratically immediately after cold start in extremely cold weather (below 20 degrees F). Affected vehicles includes 2008-2010 TT with BPY and CDMA engines, 2006-2008 A3 with BPY engine, 2006-2008 A4 with BWT engine, and A4 cabriolet with BWT engine.
The condition occurs with ambient temperature below 20 degrees F, with DTCs P0507, P2279 or P2187. Uneven idle or the engine immediately stalls prior to shifting out of Park at the first cold start. Engine operation is normal after warm-up.
It is normal for condensed water to accumulate in the engine oil during extended periods of cold weather (below freezing) and excessive vehicle short-trip operation. This water usually evaporates when the engine reaches operating temperature and exits through the crankcase ventilation system.
However, if the vehicle is mainly used for short trips and the engine does not reach operating temperature, an excessive amount of condensed water may collect in the crankcase pressure regulating valve and freeze overnight. This could lead to a temporary malfunction of the crankcase pressure regulating valve on cold engine start, and result in a rough idle or engine stall until warm crankcase gases melt the ice.
A special winter pressure regulating valve is available for vehicles in cold weather regions operated under extended short trip conditions and exhibiting these symptoms.