Universal Fault Code

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SPN 3031 (FMI 3)

MIL Lamp / Derate Imminent.

System

Exhaust (SCR)

Symptom

MIL Lamp / Derate Imminent.

Diagnosis & fix steps

LOGIC: DEF Tank Temp Sensor - Voltage Above Normal (Open Circuit). ACTION: Check for a broken wire or disconnected plug at the DEF Tank Header.

Red Seal field insights

Specs: 5V Reference. RED SEAL FIX: If the plug is green with corrosion, the 5V signal is "lost." Clean with DeoxIT. If the code persists, the internal thermistor in the header has failed.

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.

Book an uptime review

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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