Earlier this week I went to start my truck for the first time that day and the engine idled rough and I had a lot of white smoke. It slowly cleared up over the next 5 minutes and was fine the rest of the day. It has now done this for the last 4 days. The never would never smoke except on cold winter days prior to this and never this amount of smoke. The only thing I done was I used some diesel additive about 3 weeks ago and and I changed the fuel filter about 1 month ago. The eng is stock, no mods. I get a code of 500 and 1693, but i haven't figured these out yet. Any help would be appreciated. Thanks