John Deere Engines SPN3250FMI1 Fault Code: DOC Outlet Temperature Extremely Low
DOC Outlet Temperature Extremely Low · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 3250 FMI 1 sets when the John Deere engine ECU sees the diesel oxidation catalyst (DOC) outlet temperature reading lower than it should be during an active regeneration. The engine will derate, close the EGR valve, and abort the regeneration until the issue is resolved.
High severity. This is a Warning-level code, but the ECU responds by derating the engine, closing the EGR valve, and aborting regeneration. Left unresolved, incomplete regenerations can lead to DPF loading problems and repeated derates, so it should be diagnosed promptly rather than ignored.
What does John Deere Engines error code SPN3250FMI1 mean?
SPN 3250 FMI 1 means the ECU is monitoring the DOC outlet temperature sensor during an active regeneration event and the reading it gets back is lower than the temperature it expects to see. The DOC is part of the exhaust aftertreatment system, and its outlet temperature is a key signal the ECU uses to confirm that regeneration (burning off soot in the diesel particulate filter) is actually happening correctly.
When the ECU decides this signal is out of range, it treats it as a problem serious enough to intervene: it derates engine power, closes the EGR valve, and cancels the regeneration in progress. This protects the aftertreatment system and engine, but it also means reduced performance until the fault is cleared.
The two diagnostic write-ups John Deere provides for this code differ slightly in wording, but agree on the core issue: either a bad sensor, a wiring or connector problem, unintended hydrocarbons in the DOC, or ECU-side hardware or software problems can trigger it.
What triggers a John Deere Engines SPN3250FMI1 code?
The code sets when the ignition is on, the engine is running, and an active regeneration is occurring, with the DOC outlet temperature sensor signal reading lower than the ECU expects for that condition.
Common causes of SPN3250FMI1
- Bad terminals or connector at the DOC outlet temperature sensor
- Bad DOC outlet temperature sensor
- Bad ECU software
- Bad terminals or connector at the ECU
- Bad ECU
- Open or short in the harness, including a short to the signal wire
- Unintended hydrocarbons present in the DOC
- Fuel with too high a sulfur content (check operator's manual for correct fuel spec)
How to troubleshoot John Deere Engines SPN3250FMI1: first checks
- Check the connector and terminals at the DOC outlet temperature sensor (B5202) for corrosion, looseness, or damage
- Inspect the wiring harness between the sensor and the ECU for chafing, open circuits, or shorts to the signal wire
- Check the ECU connector (A5502) and terminals for a poor connection, paying attention to pin 77, which carries the common 5V sensor return circuit shared by the DOC inlet temperature sensor (B5201), DOC outlet temperature sensor (B5202), and aftertreatment pressure sensor (B5109)
- If multiple aftertreatment temperature or pressure sensor codes are active at once, suspect the shared 5V return circuit rather than three separate sensor failures
- Confirm the fuel being used meets the sulfur content specification listed in the operator's manual
- Rule out unintended hydrocarbons in the DOC as a root cause, since this can mimic a sensor or wiring fault
How the code clears
No separate clearing step is listed. Once the underlying cause (sensor, wiring, ECU, fuel quality, or hydrocarbon contamination) is corrected, the code should stop being active on the next qualifying regeneration cycle. If the fault remains active, recheck the sensor circuit and ECU connector before assuming the ECU itself is bad.
Frequently asked questions
What does SPN 3250 FMI 1 mean on a John Deere engine?
It means the ECU detected that the DOC outlet temperature sensor signal is reading a temperature lower than expected during an active regeneration event.
Will SPN 3250 FMI 1 cause a derate?
Yes. When this code is active, the ECU derates the engine, commands the EGR valve fully closed, and aborts any active regeneration.
Can bad fuel cause this code?
Yes. Running fuel with too high a sulfur content can trigger this fault. Check your operator's manual to confirm you are using the correct fuel.
Is this a sensor problem or a wiring problem?
It can be either. Possible causes include a bad DOC outlet temperature sensor, bad terminals or connectors at the sensor or ECU, an open or short in the harness, or a short to the signal wire. ECU software or hardware problems are also listed as possible causes.
Why would other sensor codes appear at the same time as SPN 3250 FMI 1?
The DOC inlet temperature sensor, DOC outlet temperature sensor, and aftertreatment pressure sensor all share a common 5V sensor return circuit at the ECU connector. A failure on that shared circuit can trigger fault codes on more than one of these sensors at once.
Does unintended hydrocarbon presence in the DOC cause this fault?
Yes, unintended hydrocarbons in the DOC are listed as one of the conditions that can cause the DOC outlet temperature reading to appear lower than expected.
Is SPN 3250 FMI 1 safe to keep driving with?
It is rated as a Warning level code, but because it causes an engine derate and aborts regeneration, you should get it diagnosed as soon as possible rather than continuing to operate normally.