2018 Freightliner Cascadia DD15 - Forced Regen Fails and Engine Derate SPN 3251 FMI 0

Question

My truck is stuck in a 5 MPH derate and I cannot get a parked regen to complete. It starts the process and ramps up RPMs but then cuts out after 10 minutes with a high pressure drop error. I am worried the DPF filters are completely baked or the DOC is face-plugged.

Sam Holloway · Accepted Answer

The issue was a completely clogged 7th injector (Hydrocarbon Doser) and a failing fuel manifold block. I replaced the doser valve (A0001401539) and the doser block assembly, which cost about $850 in parts. After installing, I ran the 'Service Routine' to prime the fuel line and the forced regen finally completed. The soot level dropped from 140% to 5% and the derate cleared immediately.

Ashley Park · Answer

Check the DOC inlet temps on your diagnostic software. If you aren't seeing at least 500-600 degrees F before the hydrocarbon doser starts spraying, the 7th injector won't even fire. You might have a stuck open thermostat keeping the engine too cool.

turbo_tony · Answer

Have you checked your intake throttle valve? If it isn't hitting the right angle during the warmup phase of the regen, the exhaust temps won't get high enough to trigger the soot burn-off, and the CPC will abort the cycle for safety.

Sarah Thompson · Answer

Perform a 'Hydrocarbon Doser Flow Test' using Detroit Diagnostic Link. It sounds like your fuel block or the doser injector itself is carboned up and not delivering enough fuel to create the heat needed for the DPF soak.

2018 Freightliner Cascadia DD15 - Forced Regen Fails and Engine Derate SPN 3251 FMI 0

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