Be careful if the check engine light is on the DEF will not regen and cause more problems ! take it back !! KevinI had the same problem shortly after the reflash. They replaced the EGR valve and MAP sensor. It was covered under the new extended warrenty. I have about 90,000 miles. Now I am contending with a low exhaust temperature warning light. The dealer said it should clear itself but it has been a week and the check engine lightis still on.