Code 1636 is super common. You might have other codes, but if you have 1636 then it is most likely the source of the problem for all those codes. Your truck can't run a regen when 1636 is active.

This is your intake manifold temperature sensor. Either the sensor has failed, the pigtail has failed, or there is corrosion in your connection. In this video we will show you how you can possibly fix things on the road to get by. Or if you can get to a Freightliner this repair is so easy we show you how to fix it permanently.