John Deere Engines SPN970FMI31 Fault Code: External Shutdown Commanded
Also called Auxiliary Engine Shutdown Switch Active, Engine Shutdown - Auxiliary Request, External Engine Shutdown Switch Active, External Shutdown Switch Activated
External Shutdown Commanded · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 970 FMI 31 means the ECU received a valid shutdown signal from an external or auxiliary engine shutdown switch and has stopped the engine. This is a programmed safety feature on OEM applications, not a default sensor fault, and it triggers a full engine STOP whenever the ignition is on and the condition is active.
Critical severity. The alarm level is listed as STOP and the control unit response is to shut the engine down. Treat any active SPN 970 FMI 31 as an immediate stop condition until the cause is found and cleared.
What does John Deere Engines error code SPN970FMI31 mean?
SPN 970 FMI 31 tells you the ECU has shut the engine down because it received an engine shutdown input voltage within the range needed to trigger a shutdown, coming from an external or auxiliary shutdown switch. On some applications the ECU instead receives this shutdown request from another controller over the CAN network rather than from a hard-wired switch.
This is a trim option, meaning the OEM built the machine with the option to wire in a customer-specified external shutdown switch. If that feature is programmed into the ECU, activating the switch, whether intentionally or due to a fault, will command a full engine shutdown. The code is really a report that the ECU did exactly what it was told to do: shut down because the shutdown circuit told it to.
Because the code can be set by a legitimate manual shutdown, a faulty switch, damaged wiring, a bad connector, or even an environmental condition acting on a mechanical linkage, diagnosis has to separate 'the switch worked as intended' from 'the switch or its circuit is broken and shutting the engine down when it should not.'
Common causes of SPN970FMI31
- A device, mechanical linkage, wiring condition, or environmental condition that caused the external shutdown switch to activate
- Bad terminals or connector at the external shutdown switch, including pinched or melted wires
- Bad terminals or connector at the ECU, or at the C08 connector
- Open or shorted wiring in the auxiliary harness or ECU harness
- Bad external shutdown switch itself
- Outdated or bad ECU software
- Bad ECU
How to troubleshoot John Deere Engines SPN970FMI31: first checks
- Check for other stored or active fault codes on the ECU and on any other machine controllers, since these can point to the actual reason the shutdown was requested
- Inspect the external shutdown switch and its connector for corrosion, looseness, or physical damage
- Trace the auxiliary and ECU harness for pinched, melted, open, or shorted wiring, paying attention to the C08 connector
- Check ECU connector terminals and connections for corrosion or poor contact
- Look for any mechanical linkage or environmental condition near the switch that could be causing an unintended activation
- Confirm current ECU software level, since outdated or bad ECU software is listed as a possible cause
How the code clears
No separate clearing step is listed beyond correcting the root cause. Since the alarm level is STOP and the ECU shuts the engine down whenever the switch or CAN request is active, the code should clear once the external shutdown switch is deactivated and any wiring, connector, switch, or software problem causing an unwanted activation is repaired. If the shutdown was intentional, no repair is needed, just deactivate the switch to resume operation.
Frequently asked questions
What does SPN 970 FMI 31 mean on a John Deere engine?
It means the ECU shut the engine down because it received a valid signal from an external or auxiliary engine shutdown switch, or in some applications a shutdown request over CAN from another controller.
Is SPN 970 FMI 31 always caused by a fault?
Not necessarily. This is a trim-programmed feature, so the code can appear because someone intentionally activated the external shutdown switch. It can also appear due to a bad switch, wiring problem, or connector issue causing an unwanted shutdown.
Will the engine restart on its own after this code sets?
No. The control unit response is to shut the engine down, and the alarm level is STOP. The engine will not run again until the shutdown switch is deactivated and, if needed, the underlying fault is fixed.
What should I check first if the engine shuts down with this code?
Check for other stored or active fault codes on the ECU and other controllers first, since they can indicate the real reason for the shutdown. Then inspect the external shutdown switch, its connector, and the related wiring and harness.
Can bad ECU software cause SPN 970 FMI 31?
Yes, outdated or bad ECU software is listed as a possible cause, along with a bad ECU itself.
Does every John Deere application have this external shutdown switch feature?
No. It is an OEM trim option. The customer has the option to have an external engine shutdown switch, and the ECU only responds to it if that feature has been programmed in.