2018 Freightliner Cascadia DD15 constant regen and derate

Question

My truck is stuck in a low-power derate and keeps asking for a parked regen every 300 miles. When it finishes the regen, the soot level stays around 40% and never fully clears. I am worried about the DPF being face-plugged since my fuel mileage has dropped significantly lately.

Kevin Tran · Accepted Answer

The issue was a completely failed Hydrocarbon Doser block. Even though I cleaned the tip, the internal valve was sticking shut. I replaced the doser block (part A0004900500) and then performed a 'DPF Ash Reset' using DiagnosticLink. Total cost was about $650 for the part and 2 hours of labor. The truck now pulls full boost and hasn't requested a regen in over 2,500 miles.

Sam Holloway · Answer

You need to check your DOC inlet temps during a parked regen. If the DOC isnt getting hot enough, it won't burn the soot out of the DPF effectively, which causes the frequent cycles.

Greg Walters · Answer

Check your EGR valve for sticking. If it is hanging open even slightly, you are creating way too much soot for the filters to handle, which will soot-load the catalyst in hours rather than days.

Jordan Lee · Answer

Have you performed a low-pressure fuel system test? If the doser valve isn't getting enough fuel pressure, it won't spray a proper mist into the exhaust stream, leading to 'wet' soot that won't burn off.

2018 Freightliner Cascadia DD15 constant regen and derate

Suggest a repair