Global SCR Fault Code
Free · no signupSPN 4334 FMI 3 / 4
Engine derate; DEF system failure; Possible white smoke from exhaust.
System
Not specified
Symptom
Engine derate; DEF system failure; Possible white smoke from exhaust.
Diagnosis & fix steps
DEF Dosing Pressure Sensor - Voltage High/Low.
LOGIC: The internal sensor in the DEF pump or line is seeing pressure outside of the 4–10 bar operating window.
ACTION: 1. Check for kinked DEF lines.
2. Inspect the DEF pump filter (usually a small screw-in mesh).
3. Check for frozen DEF in the lines.
FIX: Replace DEF Pump filter or the complete DEF Pump/Dosing Unit.
Red Seal field insights
Most people forget that DEF pumps have a service filter. If this filter gets "slime" or debris in it, the pump can't build pressure and will throw a P-code or SPN for pressure.
Same code keeps coming back?
That's a program problem, not a part problem. Book a 30-minute uptime review with Grant, a Red Seal Heavy Duty Technician.
Read before you touch anything
- This is general reference information, not a repair manual. It is for trained, qualified technicians.
- Fault codes, meanings and procedures vary by model, serial number and software version. Confirm the code and the procedure against the manufacturer's service manual before acting.
- Follow the OEM service manual, torque specs and your site's safety procedures: lockout/tagout, block raised equipment, relieve hydraulic, fuel and air pressure, and let hot systems cool.
- You use this information at your own risk. Adventure Mechanical and AM Fleet Integrity accept no liability for damage, injury, downtime or loss arising from its use.
- Not affiliated with or endorsed by any manufacturer. Brand names are used only to identify the equipment a code applies to.
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Start your free trialRelated Global SCR fault codes
- SPN 4363 FMI 0 / 16Black smoke; Poor engine performance; High exhaust backpressure.
- SPN 3364 FMI 2 / 17Engine derate; "DEF Symbol" flashing; Machine may eventually lock into 5 MPH or Idle-only.
- SPN 4364 FMI 18Progressive power loss; "Emissions Failure" warning; Excessive DEF consumption.
- SPN 3361 FMI 31Sudden shutdown or 5 MPH limit; No other active codes; Very difficult to clear.
- SPN 5246 FMI 15Dash says "Derate in 30 Minutes"; Alarm beeping; Yellow/Amber warnings.
- SPN 3216 FMI 13 / 20Intermittent Check Engine Light; Sudden derate; Inconsistent emissions data.
- SPN 5394 FMI 5"DEF System Error"; No dosing heard; DEF level stays static for days.
- SPN 3031 FMI 2 / 9DEF pump won't engage; Code appears during cold weather; High fuel use.
- SPN 1761 FMI 1 / 18Empty tank warning when full; Machine shutdown; Alarm buzzer.