Detroit Fault Code
Free · no signupSPN 4364 FMI 18
Low SCR Efficiency.
System
Exhaust
Symptom
Low SCR Efficiency.
Diagnosis & fix steps
LOGIC: NOx conversion is below 70%.
ACTION: Check for "DEF Crystallization" on the injector tip. Clean with hot distilled water.
Red Seal field insights
RED SEAL FIX: Often caused by "Lazy" NOx sensors. If the sensors are > 3 years old, they slow down and trigger this code mid-haul.
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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