SCR Conversion Efficiency - Below Normal Range
The JD-SPN4364-FMI17 (John Deere PowerTech) diesel fault code means: SCR Conversion Efficiency - Below Normal Range. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $15 DEF retest, $650-$1,400 NOx sensor, $3,500-$6,500 SCR replacement
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Common Symptoms
- DEF inducement warning -> low-idle lockout if ignored
- Failed emissions self-check
Probable Causes (Ranked by Likelihood)
- Contaminated or non-API DEF (water / wrong fluid) Very Likely
- Aged SCR catalyst (>8,000 hrs) Likely
- Leaking exhaust joint before NOx outlet sensor Possible
- Failed outlet NOx sensor Possible
Step-by-Step Diagnostic Procedure
Test DEF with refractometer (target 32.5% urea).
Smoke-test exhaust between DOC and SCR for leaks.
Swap NOx sensors (inlet <-> outlet) and re-run.
Frequently Asked Questions
What is John Deere fault code SPN 4364 FMI 17?
On John Deere PowerTech engines, SPN 4364 FMI 17 means: SCR Conversion Efficiency - Below Normal Range. Serious code -- address promptly to avoid inducement / further damage.
Can I keep using my John Deere tractor with SPN 4364 FMI 17?
Serious fault -- you can move the machine to a shop but don't run it under load. Diagnose with John Deere Service ADVISOR via an EDL v3 / CF3 interface.
How much does it cost to fix John Deere SPN 4364 FMI 17?
Repair cost range: $15 DEF retest, $650-$1,400 NOx sensor, $3,500-$6,500 SCR replacement. 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.