DPF differential pressure very high
The sensor is working and the reading is real, but the value is dangerously high. This is the engine telling you it has a mechanical or system problem, not a wiring problem.
SPN 3251 — DPF differential pressure very high
SPN 3251 is the parameter the ECM is flagging on PACCAR, Volvo, Mack, International engines. The FMI that comes with it tells you how it failed. Each failure mode below has its own causes and its own test order — do not treat them as the same repair.
DPF outlet pressure extremely high
The sensor is working and the reading is real, but the value is dangerously high. This is the engine telling you it has a mechanical or system problem, not a wiring problem.
DPF pressure data erratic with high restriction
The ECM is getting a signal but it jumps around or does not make sense. Nine times out of ten this is a connection, not a part.
DPF restriction above normal
Real reading, clearly high. Usually the middle warning stage before a derate.
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