John Deere Engines SPN110 Fault Code: Engine Coolant Temperature Signal Extremely High
Also called Coolant Temperature Signal Extremely High, Engine Coolant Temperature Extremely High, Engine Coolant Temperature High Most Severe
Engine Coolant Temperature Signal Extremely High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 110 FMI 0 sets when the ECU sees engine coolant temperature at or above the extremely high threshold, values given range from 113°C (235°F) to 118°C (244°F) depending on the application. The engine derates power and, if the shutdown feature is programmed, shuts down. Treat this as a stop-now overheat condition.
Critical severity. This is a STOP-level alarm. John Deere lists control unit response as derating maximum engine power by up to 60 percent, and if the shutdown feature is enabled the ECU will shut the engine down 30 seconds after warning code SPN 1109 FMI 31 appears. Continued operation risks major engine damage.
What does John Deere Engines error code SPN110 mean?
SPN 110 covers the engine coolant temperature (ECT) signal, and FMI 0 means the ECU has read a value that is extremely high, above the most severe threshold programmed for the engine. The ECT sensor is a thermistor mounted on the thermostat housing or rear of the cylinder head. As coolant gets hotter, the sensor's resistance drops, which lowers the input voltage the ECU sees. A very low voltage reading tells the ECU the coolant is dangerously hot.
On some applications the ECU does not read the ECT sensor directly, instead it receives coolant temperature over CAN from another controller, which measures it with its own sensor in the thermostat housing and passes the value along as a message.
Because overheating this severe can warp heads, damage bearings, or cause catastrophic engine failure, John Deere programs an automatic response: the engine derates power, and depending on how the customer configured the ECU, it may shut down entirely after a short warning period.
What triggers a John Deere Engines SPN110 code?
The threshold values differ by document and application. On OEM engines one version sets the code at 115°C (239°F). Another version sets it above 118°C (244°F). A later version splits the threshold by power rating: 113°C (235°F) on OEM engines with peak power at or above 75%, and 116°C (241°F) on OEM engines with peak power below 75%. In all cases the engine must have been running for 3 minutes before the code can set. Once active, SPN 1569 FMI 31 sets alongside it if the engine has not shut down, SPN 1109 FMI 31 sets 30 seconds before a shutdown occurs, and SPN 1110 FMI 31 sets if the shutdown feature is enabled.
Common causes of SPN110
- Internally or externally plugged radiator, or blockage on or near the radiator
- Coolant leaks or cracks in radiator hoses
- Loose or damaged cooling fan belt
- Bad or faulty radiator cap
- Improper coolant level
- Damaged fan shroud
- Excessively high ambient air temperature
- Bad thermostat
- Dirty, damaged, or poorly positioned terminals or connectors at the ECT sensor or the ECU 30-way connector
- Open or short circuit in the harness or ECT input/ground circuits
- Bad coolant temperature sensor
- Bad sensor housing, engine housing, or defective O-ring at the sensor
- Bad ECU software or a bad ECU
How to troubleshoot John Deere Engines SPN110: first checks
- Let the engine cool before opening any cap or touching cooling system components, hot coolant under pressure can cause severe burns.
- Check coolant level and condition, top off if low and look for visible leaks at hoses, the radiator, and the water pump area.
- Inspect the radiator for external blockage (debris, mud, insects) and internal blockage or plugging, especially on machines that work in dusty or dirty environments.
- Check the fan belt for looseness or damage and confirm the fan shroud is not damaged or missing, both affect airflow across the radiator.
- Inspect the radiator cap for damage or a failed seal, a bad cap can prevent the system from holding proper pressure.
- Check the thermostat for proper operation, a stuck thermostat can cause rapid, severe overheating.
- Inspect ECT sensor and ECU connector terminals for corrosion, damage, or poor seating. Use the JT07328 Connector Adapter Test Kit to probe connectors rather than forcing test probes directly into terminals, which can cause permanent terminal damage.
- Check wiring between the ECT sensor and ECU for opens, shorts, or damage, including pinched or melted sections in the harness.
- Consider ambient conditions: extremely high ambient air temperature can itself push coolant temperature into the extremely high range, especially under load.
How the code clears
No separate clearing step is listed beyond correcting the overheat condition and the underlying cause. Because the code is tied to an active overheat condition and related codes (SPN 1569 FMI 31, SPN 1109 FMI 31, SPN 1110 FMI 31) track the event in real time, the code should clear once coolant temperature drops back below the extremely high threshold and the ECU no longer sees the fault condition active. If a shutdown feature is enabled and the engine has already shut down, address the cooling system cause before restarting.
Frequently asked questions
What does SPN 110 FMI 0 mean on a John Deere engine?
It means the ECU has detected engine coolant temperature at or above the extremely high threshold for that application, ranging from 113°C (235°F) up to 118°C (244°F) depending on the engine and power rating. This is the most severe coolant temperature fault level.
Will the engine shut down when SPN 110 sets?
Only if the shutdown feature was programmed into the ECU when the machine was built. If it was enabled, the ECU derates the engine and then shuts it down 30 seconds after the warning code SPN 1109 FMI 31 appears. If the shutdown feature was not selected, the ECU applies a standard derate instead of shutting down.
How much power does the engine lose when this code is active?
John Deere's documentation lists maximum engine power derated by up to 60 percent as the control unit response, with some documents describing a derate rate that continues until the engine is running at 40% of full power.
How long does the engine need to run before this code can set?
The engine has to be running for 3 minutes before SPN 110 FMI 0 can set, according to John Deere's troubleshooting sequence.
What are the most common causes of this fault?
The most frequently cited causes are actual engine overheating (plugged radiator, low coolant, bad thermostat, damaged fan shroud, loose fan belt, bad radiator cap) and electrical faults at the ECT sensor or ECU connectors, including corroded terminals, open or shorted wiring, or a failed sensor.
Is it safe to keep driving or working with this code active?
No. This is flagged as a STOP-level alarm. Continuing to operate risks serious engine damage. Shut down safely, let the engine cool, and inspect the cooling system and related wiring before restarting.
Can a bad sensor cause this code even if the engine isn't actually overheating?
Yes. A bad ECT sensor, damaged sensor housing or O-ring, or faulty wiring and connectors can send an incorrect extremely-high signal to the ECU even when the coolant itself is not actually overheated. That's why checking connectors and wiring is a key first step alongside checking the physical cooling system.