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

Question

I am stuck in a park and my truck keeps failing the forced regen around the 15-minute mark. The dash says DPF zone 4 and I am worried it is going to go into a 5 mph derate before I can get home. The engine sounds like it is struggling to maintain the exhaust temperatures needed to finish the burn.

Brian O'Connor · Accepted Answer

The issue was a completely clogged Hydrocarbon Doser block-off valve and a leaking fuel line to the 7th injector. I replaced the Fuel Doser Valve (A0004900500) and the specific fuel line that was sucking air into the system. After the swap, I ran a parked regen and watched the DOC inlet hit 1150 degrees consistently. Total parts cost was about $550 and took 2 hours to install.

torque_terry · Answer

You might have a cracked DPF filter. Pull the temp sensor behind the DPF and look for black soot buildup; if it is black, the filters are cooked and need to be baked or replaced.

road_rambler · Answer

Listen for any air leaks near the turbo or the EGR valve. If you have an intake leak, the air-to-fuel ratio stays lean and you won't hit the 1100 degrees needed for the burn.

turbo_tony · Answer

Check your DOC inlet temperatures using DiagnosticLink. If the DOC isn't getting hot enough, the doser won't spray, and the regen will time out.

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

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