Aftertreatment DEF Doser Injector - Current Below Normal or Open Circuit
The JD-SPN4334-FMI5 (John Deere PowerTech) diesel fault code means: Aftertreatment DEF Doser Injector - Current Below Normal or Open Circuit. This is a moderate severity code.
Unverified. We could not confirm this code's definition against freely available manufacturer documentation, so treat the meaning, severity and fix guidance on this page as unconfirmed. Check it against the manufacturer's service information for your exact model and serial range before acting on it. This page is kept out of search engines for that reason, and we are working through this family manual by manual.
- Keep driving?
- Reduced power (derate)
- DIY difficulty
- intermediate
- Estimated cost
- $220-$650 DEF doser, $450-$1,400 DEF pump
What Are the Symptoms of JD-SPN4334-FMI5?
- DEF lamp on operator display / inducement countdown warning
- Loss of SCR NOx conversion efficiency (detected by OBD monitor)
- Possible engine shutdown if inducement expires
What Causes JD-SPN4334-FMI5? (Most Likely First)
- Crystallized DEF at doser / inlet flange Very Likely
- DEF pump prime failure after the tank ran dry Likely
- DEF quality out of spec (diluted with water or old fluid) Likely
- DEF line heater circuit fault in cold ambients Possible
Can I Still Drive with JD-SPN4334-FMI5?
Reduced power (derate). JD-SPN4334-FMI5 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What is John Deere fault code SPN 4334 FMI 5?
On John Deere PowerTech engines, SPN 4334 FMI 5 means: Aftertreatment DEF Doser Injector - Current Below Normal or Open Circuit. Moderate code -- diagnose soon; continued operation may increase repair scope. 8R-series DEF doser failures typically show both SPN 4334 and SPN 4363; replace doser and re-seal exhaust flange.
Can I keep using my John Deere tractor with SPN 4334 FMI 5?
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 4334 FMI 5?
Repair cost range: $220-$650 DEF doser, $450-$1,400 DEF pump. Dealer labor on large tractors runs $180-$240/hr in 2026.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose JD-SPN4334-FMI5?
Check DEF quality with a refractometer (target 32.5% urea).
Command the DEF pump in Service ADVISOR and confirm prime pressure rise.
Clean / replace the DEF doser and re-seat the exhaust flange seal.
Inspect DEF tank heater element and tank temp sensor in cold-climate failures.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
Which Vehicles Commonly Get JD-SPN4334-FMI5?
- 2015+ John Deere 7R Series (7210R, 7250R, 7290R, 7310R)
- 2015+ John Deere 8R / 8RT Series (8245R-8370R)
- John Deere S670 / S680 / S690 combines
- John Deere S770 / S780 / S790 combines
- 2021+ John Deere X9 1000 combine
- John Deere 1025R sub-compact utility tractor
- John Deere 2025R / 2038R / 2032R compact utility tractors
- John Deere R4045 / R4060 self-propelled sprayers
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