2019 GMC Sierra 3500 - SPN 3251 FMI 0 High DPF Differential Pressure

Question

Truck is down. I'm getting SPN 3251 FMI 0 which indicates the DPF pressure is way too high. The truck was doing regens more and more frequently for the last month, and today it just gave up and went into 'Speed Limited to 5 MPH' mode.

I'm terrified this is an L5P injector issue or a clogged DPF. The truck only has 65,000 miles. I don't see any exhaust leaks and the DEF fluid is fresh.

JeepJunkieJoe · Accepted Answer

✅ Confirmed fix: Found that the 9th injector (indirect fuel injector) was completely clogged with carbon, so it wasn't injecting fuel during the regen process to heat up the DPF. Because the regens were failing, the DPF got purely soot-plugged. Replaced the 9th injector and performed a service regen to clear the filter. No issues since.

KenworthKai · Answer

It sounds like your DPF is face-plugged. Sometimes a bad batch of fuel or a leaking EGR cooler can cause this. Check for coolant loss; if the EGR is leaking into the intake, it'll create a sticky soot that regens can't burn off.

2019 GMC Sierra 3500 - SPN 3251 FMI 0 High DPF Differential Pressure

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