The Dodge RAM DPF System
Your Dodge Ram is designed to burn off (clean) the diesel particulates which accumulate in the diesel particulate filter by elevating exhaust temperatures through the use of a catalyst.
Cleaning must be done to avoid damaging the diesel particular filter (DPF) and also to reduce black smoke. The cleaning process only occurs at higher road speeds (such as freeway speeds). High speed is required to clean out the diesel particulate filter.
If your Dodge Ram is driven exclusively at low speeds and in urban traffic it will require periodic trips at higher speeds to clean out the DPF. If you wait to too long to operate your Dodge Ram above 40 miles per hour, the DPF may not clean properly, and continued operation past that point may damage the DPF completely and it will require replacement.