John Deere Engines SPN174FMI3 Fault Code: Fuel Temperature Signal Out Of Range High
Also called Fuel Temperature Input Voltage High, Fuel Temperature Signal Out of Range High
Fuel Temperature Signal Out Of Range High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN174 FMI3 means the John Deere ECU sees the fuel temperature sensor input voltage above 4.9 volts, a reading that corresponds to a fuel temperature lower than what is physically possible. The ECU falls back to a limp-home fuel temperature value and slightly derates engine power. Also described as 'Fuel Temperature Input Voltage High' or 'Fuel Temperature Signal Out Of Range High'.
Medium severity. The engine keeps running on a substituted limp-home fuel temperature value and power is only slightly derated, so this is not an immediate shutdown condition. It should still be diagnosed promptly because fuel delivery is no longer being corrected for actual fuel temperature, and an open circuit or bad sensor can worsen over time.
What does John Deere Engines error code SPN174FMI3 mean?
SPN174 FMI3 points to the fuel temperature sensor circuit on John Deere engines. This sensor is a thermistor, a resistor that changes value with temperature, mounted at different locations depending on the engine (fuel filter base, injection pump fuel outlet or inlet housing, or fuel manifold depending on application). It sends a voltage to the ECU that varies with fuel temperature: higher fuel temperature gives a lower voltage, lower temperature gives a higher voltage.
The ECU uses this signal to fine-tune fuel delivery for changes in fuel density caused by temperature swings. When the input voltage climbs above the sensor's high voltage specification of 4.9 volts, that reading maps to a fuel temperature colder than is physically possible, so the ECU flags it as an out-of-range fault rather than trusting the signal.
Because the circuit is designed so that voltage rises as resistance to ground increases, the most likely cause of this fault is an open circuit somewhere in the sensor, its connector, or the wiring. A short from the 5-volt input wire to a power source is possible but less likely.
What triggers a John Deere Engines SPN174FMI3 code?
The fault sets when the fuel temperature input voltage exceeds the sensor's high voltage specification, listed as 4.9 volts for OEM engine applications. This voltage corresponds to a fuel temperature that is lower than what is physically possible, which is how the ECU recognizes the signal as invalid rather than a real cold-fuel reading. Other applications may use a different high-voltage specification listed in the engine's application specifications.
Common causes of SPN174FMI3
- Dirty, damaged, or poorly positioned terminals at the fuel temperature sensor connector
- Dirty, damaged, or poorly positioned terminals at the ECU connector (30-way or 60-way depending on application)
- An open or short in the wiring harness between the ECU and the fuel temperature sensor
- An open in the fuel temperature ground circuit
- An open in the fuel temperature input circuit
- A failed fuel temperature sensor
- A failed ECU
How to troubleshoot John Deere Engines SPN174FMI3: first checks
- Without disconnecting anything yet, visually inspect the ECU connector and fuel temperature sensor connector for contamination, damage, or terminals that are not fully seated
- Check the wiring harness between the ECU and sensor for visible damage, chafing, or corrosion
- Locate the fuel temperature sensor for your engine (fuel filter base, injection pump fuel inlet or outlet housing, or fuel manifold, depending on application) and inspect its connector closely
- If probing connector terminals is needed, use a proper connector adapter test kit rather than forcing probes into the terminals, since forcing probes can damage them and create a new fault
- Test the sensor circuit for an open condition first, since an open circuit is the more probable cause of a voltage-high fault on this circuit
- Check for a short from the 5-volt input wire to a power source if no open is found
How the code clears
No separate clearing step is listed. Repair the underlying wiring, connector, or sensor problem, then verify the fault does not reset once the fuel temperature input voltage returns to a normal range. No reset procedure is listed for this code beyond fixing the root cause.
Frequently asked questions
What does SPN174 FMI3 mean on a John Deere engine?
It means the ECU detected the fuel temperature sensor's input voltage rise above 4.9 volts, a level corresponding to a temperature colder than fuel can physically be, so the signal is treated as out of range.
Can I keep running the machine with this code active?
The engine will keep running using a limp-home fuel temperature value, and power may be slightly derated. It is not listed as an immediate shutdown fault, but the fuel delivery correction for actual fuel temperature is lost until the fault is fixed, so it should be diagnosed soon.
What limp-home value does the ECU use for this code?
This varies by application. Some versions use a flat default of 40°C (104°F). Others use -20°C (-4°F) during cranking and 40°C (104°F) during running, and some later versions default to 90°C (194°F). Check the specific engine's documentation for the exact value used.
Where is the fuel temperature sensor located?
The location depends on the engine application. It can be on the base of the fuel filter, on the injection pump fuel outlet or inlet housing, or on the fuel manifold. It is a thermistor that changes resistance with fuel temperature.
What is the most likely cause of this fault?
An open circuit is the most probable cause, since the circuit is designed to see voltage rise as resistance to ground increases. A short from the 5-volt input wire to a power source is possible but less common.
Is it safe to probe the connector terminals directly to test this circuit?
No. Forcing test probes into the connector terminals can damage them. Use a proper connector adapter test kit to make measurements without damaging the terminals.
Will fixing this code require replacing the ECU?
Not usually. Bad terminals, connector contamination, or an open or short in the harness are more common causes than a bad sensor or a bad ECU. Rule out wiring and connector issues first before considering sensor or ECU replacement.