2011 GMC Sierra 2500HD - SPN 3251 FMI 0 - DPF Pressure High

Question

My LML Duramax is throwing an SPN 3251 FMI 0 code, which my scanner says is 'Particulate Trap Differential Pressure extremely high'. The truck is in limp mode and telling me I have 0 miles before speed is limited to 5 MPH.

I tried to force a service regen with my tool, but it fails immediately because the exhaust backpressure is too high to safely start the process. I really don't want to replace the whole DPF if I don't have to.

TireGuyTrevor · Accepted Answer

✅ Confirmed fix: The DPF was 100% face-plugged with soot. I had to remove the DPF and send it to a professional cleaning facility for a 'bake and blast' service. While it was out, I found the 9th injector was completely blocked with carbon. Replaced the 9th injector and reinstalled the clean DPF. Logged a successful forced regen and the pressure drop is now within spec.

EuroEricaW · Answer

If you're getting 'extremely high' pressure and can't start a regen, your 9th injector (Hydrocarbon Injector) is likely clogged. If that injector can't spray fuel into the exhaust during the regen cycle, the DPF never gets hot enough to burn the soot, and eventually, it just plugs up solid.

2011 GMC Sierra 2500HD - SPN 3251 FMI 0 - DPF Pressure High

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