Universal Fault Code

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SPN 3364 (FMI 2/17)

MIL Lamp / 5-MPH Derate.

System

Exhaust (SCR)

Symptom

MIL Lamp / 5-MPH Derate.

Diagnosis & fix steps

LOGIC: DEF Quality Sensor detects Urea concentration is outside the 32.5% ± 3% window. ACTION: Test the DEF with a Refractometer. If it tests 32.5%, the sensor is "drifting."

Red Seal field insights

Specs: Target: 32.5% Urea. PRO-TIP: "Old" DEF (stored in the sun) breaks down into ammonia and water. If it smells like a gym locker, it’s toast. Drain and flush the tank.

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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