Aftertreatment SCR Inlet Temperature - Voltage Below Normal or Shorted to Low Source
The JD-SPN4360-FMI4 (John Deere PowerTech) diesel fault code means: Aftertreatment SCR Inlet Temperature - Voltage Below Normal or Shorted to Low Source. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- advanced
- Estimated cost
- $260-$780 NOx sensor / SCR temp sensor, $3,500-$7,500 SCR catalyst
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Common Symptoms
- SCR NOx-efficiency fault, derate within one drive cycle if persistent
- Low tailpipe NOx conversion at operating temp
- Dealer-inducement warnings on Tier 4 Final machines
Probable Causes (Ranked by Likelihood)
- Upstream / downstream NOx sensor drift Likely
- SCR inlet / outlet temperature sensor failure Likely
- SCR substrate poisoning (wrong DEF) or thermal damage Possible
- Exhaust leak upstream of SCR disturbing sensor reading Possible
Step-by-Step Diagnostic Procedure
Record SCR inlet vs. outlet temperature during steady-state high idle.
Use Service ADVISOR SCR efficiency test -- compare to CTM acceptance band.
Inspect clamps / V-bands between turbo and SCR for leaks.
If substrate is damaged, only a full catalyst module replacement will clear the code.
Frequently Asked Questions
What is John Deere fault code SPN 4360 FMI 4?
On John Deere PowerTech engines, SPN 4360 FMI 4 means: Aftertreatment SCR Inlet Temperature - Voltage Below Normal or Shorted to Low Source. Moderate code -- diagnose soon; continued operation may increase repair scope.
Can I keep using my John Deere tractor with SPN 4360 FMI 4?
Moderate fault -- you can usually keep working but expect derate if aftertreatment-related. Diagnose with John Deere Service ADVISOR via an EDL v3 / CF3 interface.
How much does it cost to fix John Deere SPN 4360 FMI 4?
Repair cost range: $260-$780 NOx sensor / SCR temp sensor, $3,500-$7,500 SCR catalyst. Dealer labor on large tractors runs $180-$240/hr in 2026.
Sources
This page is built from documented references. Verify against your own service info before repair work.