John Deere Engines SPN110FMI16 Fault Code: Engine Coolant Temperature Signal Moderately High
Also called Coolant Temperature Signal Moderately High, Engine Coolant Temperature High Moderately Severe, Engine Coolant Temperature Moderately High
Engine Coolant Temperature Signal Moderately High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 110 FMI 16 means the ECU has detected engine coolant temperature above its moderately high warning threshold, ranging from 104°C (219°F) to 113°C (235°F) depending on the application. This triggers engine protection derate. It is not an immediate shutdown code, but it means the engine is running hotter than it should and needs attention before it gets worse.
High severity. This code does not shut the engine down, but it activates an automatic power derate and signals a real overheating condition or a sensor/wiring fault reporting one. Left unaddressed, coolant temperature can climb into the extremely high range, which triggers SPN 110 FMI 0 and a more severe derate or shutdown. Treat it as a stop-soon condition, not a running repair.
What does John Deere Engines error code SPN110FMI16 mean?
SPN 110 FMI 16 is set by the engine's ECU when the Engine Coolant Temperature (ECT) sensor signal, or a coolant temperature value received over CAN from another controller, reads above a moderately high warning setpoint. The ECT sensor is a thermistor mounted on the thermostat housing (on some engines, at the rear of the cylinder head) that varies its resistance with temperature. Higher coolant temperature produces a lower input voltage to the ECU, and lower temperature produces a higher voltage.
This is a moderate warning level, one step below the more severe FMI 0 overheat code. The ECU responds by enabling engine protection, which reduces available power on a timed ramp until the engine is running at a reduced percentage of rated power. If coolant temperature drops back below the moderately high value, power is restored gradually. If it instead climbs into the extremely high range, the ECU escalates to SPN 110 FMI 0 with a harsher derate or shutdown.
Because the same fault code can be triggered either by a genuinely overheating engine or by a bad sensor, wiring, or connector reporting a false high reading, diagnosis has to rule out both a real cooling system problem and an electrical fault before parts get replaced.
What triggers a John Deere Engines SPN110FMI16 code?
The ECU sets SPN 110 FMI 16 when it senses engine coolant temperature above a moderately high setpoint. The exact threshold varies by application: 108°C (226°F), 104°C (219°F), 113°C (235°F), and 105°C (221°F) all appear as the moderately high specification depending on the specific engine and OEM configuration. Once triggered, engine protection derates power at a rate of 2% per minute, 20% per minute, or 40% per minute depending on the application, continuing until the engine reaches a reduced power level of 60% of full power, 80% of full power, or a total reduction of 20% of rated power, again depending on configuration. If coolant temperature falls back below the moderately high value, power is restored at 2% per minute until full power is reached. If temperature instead rises further, SPN 110 FMI 0 sets with a more severe response.
Common causes of SPN110FMI16
- Dirty, damaged, or poorly positioned terminals at the ECU connector (described as a 30-way or 60-way connector depending on application)
- Dirty, damaged, or poorly positioned terminals at the ECT sensor connector
- Bad or open ECT sensor input or ground circuits, including open or short conditions in the wiring harness between the ECU and the sensor
- A bad or failed ECT sensor itself
- An actual engine overheating condition, meaning the cooling system is not keeping the engine within normal operating temperature
How to troubleshoot John Deere Engines SPN110FMI16: first checks
- Let the engine cool before opening the cooling system or touching hoses and the radiator cap. Hot coolant under pressure can cause serious burns.
- Without disconnecting anything, visually inspect the ECU connector and the ECT sensor connector for contamination, corrosion, damage, or terminals that are pushed back or poorly seated.
- Check the wiring harness between the ECU and the ECT sensor for chafing, pinches, or damage that could cause an open or short circuit.
- Compare the reported coolant temperature to the actual engine condition: if the temperature is at or above the specification and the engine is genuinely running hot, treat it as a real overheating problem and check coolant level, radiator condition, fan operation, water pump, thermostat, and for airflow restrictions.
- If the reported temperature is significantly lower than what the fault would suggest, verify the ECT sensor input and return circuits are good. If those circuits check out, the sensor itself is likely bad and should be replaced, then retest.
- When probing connectors for voltage or resistance checks, use a proper connector adapter test kit rather than forcing probes into the terminals, since forcing probes can damage the terminals and create a new fault.
How the code clears
No separate clearing step is listed beyond correcting the cause. Once the coolant temperature drops back below the moderately high setpoint, the ECU restores power gradually at the stated rate until full power is achieved. If the underlying cause was a bad sensor, connector, or wiring fault, repairing or replacing that component and confirming a normal, stable temperature reading should allow the code to clear on its own during normal operation.
Frequently asked questions
Can I keep driving or working with SPN 110 FMI 16 active?
You can, but the ECU will be actively reducing engine power, and if the coolant temperature keeps climbing you risk it setting the more severe SPN 110 FMI 0, which brings a harsher derate or shutdown. It is best treated as a stop-soon issue: get the machine to a safe place, let it idle or cool as needed, and diagnose before continuing heavy work.
What temperature triggers this code on John Deere engines?
It depends on the application. Different John Deere engine configurations list the moderately high threshold at 108°C (226°F), 104°C (219°F), 113°C (235°F), or 105°C (221°F). Check the application specifications for your specific engine to confirm the exact setpoint.
Is this the same as an engine overheating shutdown code?
No. SPN 110 FMI 16 is a moderate warning that triggers a power derate, not a shutdown. If coolant temperature keeps rising past the moderately high value into the extremely high range, the ECU sets a separate code, SPN 110 FMI 0, which brings a more severe derate and possibly a shutdown.
How much power will I lose when this code is active?
That depends on the application's derate configuration. Some engines reduce power by 2% per minute until power is down by 20% of rated power or the engine is at 80% of full power. Others derate faster, at 20% per minute or 40% per minute, down to 60% of full power. Power is restored at 2% per minute once temperature drops back below the moderately high setpoint.
Could this code be a false alarm from a bad sensor instead of real overheating?
Yes. A bad ECT sensor, corroded or damaged connector terminals, or an open or shorted circuit between the ECU and the sensor can all cause the ECU to see a falsely high temperature reading. If the actual engine does not feel or act like it is overheating, check the sensor circuits and connectors before assuming a cooling system failure.
What should I check first when this code comes up?
Start with a visual inspection of the ECU connector and the ECT sensor connector for dirty, damaged, or poorly seated terminals, and check the wiring harness between them for damage. Then compare the reported temperature against the actual engine condition to determine whether you are dealing with a real overheating problem or an electrical fault.
Do I need special tools to check the ECT sensor wiring?
Yes, it is recommended to use a proper connector adapter test kit designed for this purpose rather than forcing meter probes directly into the connector terminals. Forcing probes into terminals can damage them and create additional wiring problems.