2018 Freightliner Cascadia DD15 constant DPF regen cycles and derate 5MPH

Question

My truck is stuck in a forced parked regen loop every couple hundred miles and now I am getting a 5 MPH derate warning on the dash. The regen finishes successfully but the soot level climbs back to high within 4 hours of driving under load. I can hear a slight whistling under the hood when the turbo spoils up but I cannot locate a visible leak.

wrenchqueen · Accepted Answer

The issue was a cracked One-Box assembly internal partition and a leaking bellows pipe between the turbo and the aftertreatment inlet. Replaced the bellows pipe (Part #A6804910480) and found the DOC was face-plugged with oil ash. After replacing the bellows and having the DPFs professionally baked and cleaned, I performed a 'DOC/DPF Efficiency Test' in DiagnosticLink to reset the ash accumulators and clear the 5MPH derate. Total cost for parts and cleaning was about $3,200.

garagegrease · Answer

Have you performed a smoke test on the intake side? High soot loading is usually caused by an 'air-starved' condition. If your turbo isn't putting out enough boost or you have a small charge air cooler leak, you'll run rich and clog that DPF fast.

shoptech_carlos · Answer

Check your EGR valve operation using DiagnosticLink. If the valve is sticking partially open, you are recirculating too much exhaust gas which increases particulate matter. Also, check your intake manifold pressure sensor for carbon buildup.

Pete Sanders · Answer

Look at your DOC inlet temperatures during the regen. If you aren't hitting at least 550 degrees Celsius, the DPF isn't actually oxidizing the soot properly, which explains why the soot gauge stays high.

2018 Freightliner Cascadia DD15 constant DPF regen cycles and derate 5MPH

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