2018 Freightliner Cascadia DD15 - Forced Regen Fails at 60% - Code SPN 3251 FMI 0

Question

My truck is stuck in a 5 mph derate and I can't get a parked regen to complete. Every time it gets about 20 minutes into the process, the exhaust temperature drops and the sequence just cancels without an error message on the dash. I am worried the DPF is completely baked or the 7th injector is clogged.

Ashley Park · Accepted Answer

The issue was a failed Hydrocarbon Dosier Valve (Part #A0004900913). The nozzle was completely carbon-coked and wasn't atomizing the fuel, so the DOC couldn't light off properly. I replaced the dosier valve, performed a 'Service Aftertreatment System' reset in DiagnosticLink 8.0, and the forced regen completed successfully in 45 minutes. Total cost for the part was about $380.

turbo_tony · Answer

It sounds like a fuel dosing issue. If the Hydrocarbon Injector (7th injector) is carboned up, it can't spray enough diesel into the DOC to maintain the heat required for the DPF soot oxidation.

Jake Morrison · Answer

Have you looked at your DOC inlet temps? If the DOC is face-plugged, you will never get the DPF hot enough. You need to pull the bellows pipe and look at the face of the catalyst.

Chris Donovan · Answer

Check your Delta P sensor and the tubes leading to it. If those tubes are pinched or clogged with soot, the MCM won't see the pressure drop it expects during the burn and will kill the cycle for safety.

2018 Freightliner Cascadia DD15 - Forced Regen Fails at 60% - Code SPN 3251 FMI 0

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