SPN 411 FMI 3 — EGR Differential Pressure — Voltage High
The EGR differential-pressure sensor signal is high/out of range. The ECM may limit EGR flow and stage a derate. Usually it's soot-plugged sensor tubes, a sensor fault, or wiring — not always a failed EGR valve.
Your SPN/FMI rides along, so nearby mechanics see the fault before they quote you.
How serious is it?
Caution. Limp to the next safe stop.
Most likely causes
- Soot-packed or plugged EGR pressure sensor tubes/ports
- Failed EGR differential-pressure sensor
- Short-to-voltage or chafed signal wiring
- Sticking EGR valve affecting the pressure reading
First moves (roadside)
- Inspect and clean the EGR pressure sensor tubes — soot packing is extremely common here.
- Check the connector and signal wire for a short-to-voltage before replacing the sensor.
- Look for companion EGR valve/position codes that point to the valve itself.
- Verify the reading against actual conditions before condemning parts.
Common misdiagnoses
- Replacing the EGR valve when only the sensor tubes were soot-plugged.
- Condemning the sensor when the harness was shorted high.
- Clearing the code without cleaning the cause of the restriction.
FAQ
The EGR differential-pressure sensor signal is high/out of range. The ECM may limit EGR flow and stage a derate. Usually it's soot-plugged sensor tubes, a sensor fault, or wiring — not always a failed EGR valve.
Caution — Limp to the next safe stop.
The most common cause is: Soot-packed or plugged EGR pressure sensor tubes/ports. Other possibilities include Failed EGR differential-pressure sensor; Short-to-voltage or chafed signal wiring; Sticking EGR valve affecting the pressure reading.
Limp to the next safe stop. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Find a mechanic or related guides
General diagnostic guidance for heavy-duty diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack). Not a substitute for a scan-tool diagnosis on your specific truck.