John Deere Engines SPN107FMI31 Fault Code: Air Filter Restriction Switch Activated
Also called Air Filter Restriction Detected, Air Filter Restriction High, Air Filter restriction Switch Activated
Air Filter Restriction Switch Activated · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 107 FMI 31 means the John Deere ECU has detected that the air filter restriction switch (also called the air vacuum switch) has activated, telling the ECU the air filter is restricted. The engine may derate as a result. This is set any time the engine is on and the fault is active.
Medium severity. This code triggers an engine protection response on OEM applications, with derate to 80% of full power or an outright 50% power derate depending on the application programming. It will not shut the engine down, but ignoring it costs power and can lead to rough running or black smoke. Diagnose and fix promptly, ideally before the next haul or heavy work cycle.
What does John Deere Engines error code SPN107FMI31 mean?
SPN 107 FMI 31 is set when the ECU sees that the air filter restriction switch, sometimes called the air vacuum switch, has been activated because of high resistance to airflow through the air filter. This switch sits on the clean side of the air filter, downstream of the filter media, and closes its contacts when air pressure there rises due to a clogged or restricted filter.
This feature is a customer-selected trim option. Not every John Deere engine setup has this switch enabled, but where it is programmed into the ECU, the controller responds to the switch activating by cutting engine power. Depending on the application, the ECU may derate the engine by 50% of full power immediately, or ramp the derate down gradually at 2% per minute until the engine is running at 80% of full power.
Symptoms an operator may notice include reduced power, rough running, or black exhaust smoke coming from the stack. There is no shutdown feature tied to this code, so the engine keeps running, just at reduced output, until the restriction is cleared or the fault clears itself.
What triggers a John Deere Engines SPN107FMI31 code?
The code sets whenever the engine is on and the air filter restriction switch or air vacuum switch contacts close due to the ECU sensing high air pressure on the clean side of the filter, indicating restricted airflow through the filter system.
Common causes of SPN107FMI31
- Plugged air filter or restricted inlet tube, inlet piping, or intake air piping
- Restrictions in the dust valve, suction side of the turbo, or elsewhere in the filter system
- Bad air filter (damaged, wrong part, or worn out media)
- Bad air filter restriction switch or air vacuum switch itself
- Bad terminals or connector at the air filter restriction switch or vacuum switch
- Bad terminals or connector at the C08 connector or at the ECU connector
- Open or short in the main wiring harness or auxiliary harness
- Outdated or bad ECU software
- Bad ECU
How to troubleshoot John Deere Engines SPN107FMI31: first checks
- Visually inspect the air filter element for dirt, debris, or damage, and replace it if restricted before doing any further electrical diagnosis
- Check the inlet tube, intake piping, and dust valve for blockages, collapsed sections, or debris that could be restricting airflow ahead of the filter
- Inspect the air filter restriction switch or air vacuum switch and its connector for dirty, damaged, loose, or corroded terminals
- Trace the harness between the switch and the ECU, including the C08 connector, looking for chafed wires, opens, or shorts
- Check the ECU connector itself for damaged or poorly seated pins
- Confirm ECU software is current, since outdated software is a listed possible cause
How the code clears
No separate clearing step is listed beyond fixing the root cause. Once the restriction is cleared, whether that means replacing the air filter, clearing an obstruction in the intake tubing, or repairing a bad switch or wiring connection, the switch should open again and the ECU should stop seeing the high air pressure condition, allowing power to return to normal. For exact procedures, consult the application troubleshooting manual, since it is referenced directly for this code.
Frequently asked questions
What does SPN 107 FMI 31 mean on a John Deere engine?
It means the ECU has detected that the air filter restriction switch, or air vacuum switch, has activated because airflow through the air filter is restricted. The engine is on and the fault is currently active.
Will SPN 107 FMI 31 shut down my engine?
No. There is no shutdown feature tied to this code. Instead, on applications with the derate feature enabled, the engine will lose power, either an immediate 50% derate or a gradual derate of 2% per minute down to 80% of full power, depending on how the OEM application is programmed.
Why is my engine losing power and smoking black smoke with this code?
A restricted air filter starves the engine of clean air, which can cause rough running, reduced power, and black exhaust smoke. The ECU also actively derates power as an engine protection response once the switch activates.
Do all John Deere engines have this air filter restriction switch?
No. It is a customer-selected trim option programmed into the ECU. Only applications with this feature enabled will set SPN 107 FMI 31 and respond with a derate.
What should I check first if I get this code?
Start with the air filter itself. Replace it if it is dirty or restricted, then check the inlet tubing and dust valve for blockages. If the filter and intake are clear, move on to checking the switch, its connector, and the wiring harness back to the ECU.
Can bad wiring or a bad ECU cause this code even with a good air filter?
Yes. Listed causes include bad terminals or connectors at the switch, at the C08 connector, or at the ECU, along with opens or shorts in the harness, outdated ECU software, or a bad ECU itself. If the filter and intake are clean, these are the next things to check.