We have had some cold weather in the last few months, today showing -24C on the truck thermo. The truck started just fine and I let it warm up for about 10 min while I got a coffee and a quick bite, however when I came back the exhaust from the truck smelled so bad. It could be that the DEF is frozen and is not doing its job, but I could smell a terrible sour smell from over 30 feet away. I could smell it for a few minutes while in the cab, but once I got to work it was fine. Anyone else encounter this?