John Deere Fault Code
Free · no signupSPN 4364 FMI 18
AdBlue Warning Light / Heavy Derate
Variant 1
System
Emissions / SCR
Symptom
AdBlue Warning Light / Heavy Derate
Diagnosis & fix steps
LOGIC: SCR NOx Conversion Efficiency Low (Downstream Sensor Reading High).
ACTION: Check DEF quality with a refractometer (32.5% spec). Inspect DEF dosing injector for crystallization/clogging. Check for exhaust leaks upstream of NOx sensor.
Red Seal field insights
Conversion Failure: Trailing downstream NOx sensor data remains too close to inlet NOx logs, indicating the catalyst is failing to split emissions.
Variant 2
System
Aftertreatment
Symptom
Derate Warning / Selective Catalytic Reduction
Diagnosis & fix steps
LOGIC: SCR NOx Conversion Efficiency Low (Downstream Sensor Reading High).
ACTION: Check for exhaust leaks upstream of NOx sensor. Perform active DPF/SCR manual regeneration and verify DEF pressure remains stable at ~9 bar (~130 PSI).
Red Seal field insights
Common Fail: Soot or oil film buildup on downstream NOx sensor probe face; clean probe with zero-residue cleaner or replace sensor.
Variant 3
System
Aftertreatment
Symptom
Derate Warning / Selective Catalytic Reduction
Diagnosis & fix steps
LOGIC: SCR NOx Conversion Efficiency Low (Downstream Sensor Reading High).
ACTION: Check for exhaust leaks upstream of NOx sensor. Perform active DPF/SCR manual regeneration and verify DEF pressure remains stable at ~9 bar (~130 PSI).
Red Seal field insights
Common Fail: Soot or oil film buildup on downstream NOx sensor probe face; clean probe with zero-residue cleaner or replace sensor.
Track this across your whole fleet
This code is free to read. AM Fleet Integrity lets your team log fault codes against assets, plus the full fault-code library, QR operator reporting, PM scheduling and predictive alerts. Start free — no credit card required.
Start your free trial