John Deere Engines SPN110FMI4 Fault Code: Engine Coolant Temperature Signal Out of Range Low
Also called Coolant Temperature Signal Out of Range Low, Engine Coolant Temperature Input Voltage Low
Engine Coolant Temperature Signal Out of Range Low · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 110 FMI 4 (also shown as DTC 110.04) sets when the engine coolant temperature (ECT) sensor input voltage drops below the sensor's low voltage specification, which corresponds to a coolant temperature that is physically impossible. The ECU responds by defaulting the ECT reading and disabling high-coolant-temperature engine protection, and it lights a blinking warning lamp on some applications.
High severity. The code itself does not stop the engine, but it disables the ECU's high coolant temperature protection feature. That means an actual overheating condition could go undetected while this fault is active. Diagnose it before it masks a real overheat.
What does John Deere Engines error code SPN110FMI4 mean?
SPN 110 FMI 4 points to the engine coolant temperature circuit reporting a voltage that is too low to be real. The ECT sensor is a thermistor mounted on the thermostat housing. Its resistance changes with coolant temperature, and that resistance change is what causes the input voltage seen by the ECU to rise and fall: hotter coolant produces a lower voltage, colder coolant produces a higher voltage.
When the input voltage falls below the sensor's low voltage specification, the ECU knows the reading can't be real, because that voltage would correspond to a coolant temperature that is higher than what is physically possible. Since the circuit is designed to show a voltage drop as resistance to ground decreases, the most likely underlying cause is low resistance to ground, in other words a grounded or shorted circuit.
Once the code sets, the ECU stops trusting the live sensor signal and substitutes a default value so the engine can keep running. Depending on the application and operating mode, the default value used in start mode and running mode differs, and the ECU's high coolant temperature engine protection feature is disabled. This is why the fault needs attention promptly even though it doesn't itself force a shutdown.
What triggers a John Deere Engines SPN110FMI4 code?
The code sets when the ECT input voltage drops below the sensor's low voltage specification. For OEM engine applications this specification is listed as 0.3 volts in one version of this diagnostic and 0.1 volts in other versions and later manual revisions; other applications should be checked against the application-specific specification table. This voltage corresponds to a coolant temperature reading that is higher than what is physically possible, which is how the ECU recognizes the signal as invalid rather than real data.
Common causes of SPN110FMI4
- Dirty, damaged, corroded, or poorly positioned terminals or connector at the ECU (described in various versions as the ECU connector, the 60-way ECU connector, or the 30-way ECU connector)
- Dirty, damaged, or poorly positioned terminals or connector at the ECT sensor
- Open or short in the wiring/harness circuits running to the ECT sensor, most likely a short to ground given how the circuit is designed
- Bad or failed ECT sensor (internal thermistor fault)
- Bad or faulty ECU
How to troubleshoot John Deere Engines SPN110FMI4: first checks
- Before disconnecting anything, visually inspect the ECU connector(s) and the ECT sensor connector for contamination, corrosion, damage, or terminals that are pushed back or poorly seated.
- Inspect the full length of wiring between the ECU and the ECT sensor for chafing, pinches, or exposed conductors that could be shorting to ground.
- If SPN 1080 FMI 4 is also present, work through that code's diagnostic procedure first before continuing with SPN 110 FMI 4, since it may be the root cause.
- Check the ECT sensor itself for a failed thermistor once wiring and connectors are confirmed good.
- Use a proper connector adapter test kit rather than probing terminals directly. Forcing test probes into connector terminals can damage them and create a new intermittent fault.
How the code clears
No separate clearing step beyond fixing the underlying wiring, connector, sensor, or ECU fault is listed. Once the ECT input voltage returns to a valid range and stays there, the ECU should stop substituting the default temperature value and restore the high coolant temperature engine protection feature. No dedicated reset procedure is listed for this code.
Frequently asked questions
What does John Deere SPN 110 FMI 4 mean?
It means the ECU is seeing an engine coolant temperature sensor input voltage that is below the sensor's low voltage specification, which corresponds to a temperature that isn't physically possible. The ECU flags this as an invalid signal rather than trusting it.
Is it safe to keep driving or running the equipment with this code active?
The engine will keep running because the ECU substitutes a default coolant temperature value, but the ECU's high coolant temperature engine protection feature gets disabled while the code is active. That means a real overheat could go unnoticed. It's best treated as a High priority fault to diagnose promptly rather than ignore.
What is the low voltage specification that triggers this fault?
Different versions of this diagnostic list the OEM low voltage specification as 0.3 volts or 0.1 volts depending on the manual revision and application. Other applications should be checked against their specific low ECT input voltage specification table.
What does the ECU do once this code sets?
The ECU substitutes a default coolant temperature value instead of the live sensor reading. Depending on the version and operating mode, defaults range from -30°C (-22°F) or 0°C (32°F) in start mode up to 90°C (194°F) or 95°C (203°F) as a running or limp-home value. A blinking warning light may also come on.
What is the most likely root cause of this fault?
Because the circuit is designed to see a voltage drop as resistance to ground decreases, the most probable cause is a short to ground or low resistance to ground somewhere in the ECT sensor circuit, though bad connectors, an open harness, a failed sensor, or a faulty ECU are all listed as possible causes.
Should I check for other codes before working on SPN 110 FMI 4?
Yes. If SPN 1080 FMI 4 is present at the same time, that diagnostic procedure should be followed first, since it may explain or resolve the SPN 110 FMI 4 fault.
Can I just probe the connector terminals with a multimeter to test this?
Forcing test probes directly into connector terminals can damage them. A proper connector adapter test kit is recommended so measurements can be taken without harming the terminals.