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SPN 4334 FMI 3 — DEF pump pressure sensor — voltage high
SeriousAftertreatmentPower derate likely — plan to stop soon
Applies to: Detroit · Sae
DEF pump pressure sensor — voltage high.
Don't risk it — get a diesel tech on the truck.
Look up listed providers near you and give them this SPN/FMI when you call.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Open sensor
- Signal short high
- Sensor failed
First moves (roadside)
- Unplug sensor — invert fault
- Unplug sensor
FAQ
What does SPN 4334 FMI 3 mean?
DEF pump pressure sensor — voltage high.
How serious is SPN 4334 FMI 3?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of SPN 4334 FMI 3?
The most common cause is: Open sensor. Other possibilities include Signal short high; Sensor failed.
Can I keep driving with SPN 4334 FMI 3?
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Throwing this code right now?
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.