SCR SYSTEM FAULT 805256 STORED IN VERY COLD WEATHER. After the vehicle is exposed to prolonged temperatures under -9°C (15.8°F) and is then driven a long distance when temperatures are above -9°C (15.8°F), the check engine light may be illuminated. The following fault may be stored in the Digital Diesel Electronics (DDE) 805256 - Active tank filling level sensor, signal: echo fault In low temperature under -9°C (15.8°F) a layer of ice may form in the active tank. This can result in an incorrect level measurement after the vehicle is driven.
