My truck seems to be stuck in regen. Unloaded: city egt's are about 900, highway 1,000+. On the highway will be 1000 then go to 1200 in about 2 seconds. Stay there for about 5 seconds then go back to 1000. OR it will just stay around 1000 but doesn't get any less than 1000 deg. on the highway. Has been doing this for a few days over about 150 or so miles. What the deal? Thanks.