Caterpillar Fault Code
Free · no signupSPN 3251 FMI 0
Active Derate Warning / DPF Light
System
Emissions / DPF
Symptom
Active Derate Warning / DPF Light
Diagnosis & fix steps
LOGIC: DPF Differential Pressure Extremely High (Soot Load Level 3).
ACTION: Execute forced manual DPF park regeneration via service tool. Inspect pressure sensor sensing lines for soot blockages or moisture condensation.
Red Seal field insights
Exhaust Restriction: High soot density builds exhaust backpressure, restricting turbo spooling and forcing the ECU into an active regeneration requirement.
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