John Deere Engines SPN105FMI16 Fault Code: Manifold Air Temperature Signal Moderately High
Also called Intake Manifold Air Temperature Signal Moderately High, Manifold Air Temperature Moderately High
Manifold Air Temperature Signal Moderately High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 105 FMI 16 means the John Deere ECU sees intake manifold air temperature above its warning set point, commonly cited as 88°C (190°F) in most applications, with other application values ranging up to 100°C (212°F) or 120°C (248°F) for T engines, and 90°C (194°F) on some OEM setups. The engine responds by derating power, and SPN 1569 FMI 31 may also appear alongside it.
High severity. This is an engine protection code, not an immediate shutdown code. The ECU will not shut the engine down for this fault, but it will derate power, commonly at 2% per minute until the engine reaches 80% of full power. Left unaddressed, the derate limits productivity and signals a real cooling or airflow problem that can lead to further engine stress.
What does John Deere Engines error code SPN105FMI16 mean?
SPN 105 FMI 16 tells you the John Deere engine control unit (ECU) is reading manifold air temperature (MAT) higher than the warning threshold programmed into it. The MAT sensor is a thermistor mounted in the intake manifold. As intake air gets hotter, the sensor's resistance drops, which lowers the voltage signal the ECU sees. The ECU uses this reading, often together with the manifold air pressure (MAP) sensor, to figure out how much air is going into the engine and whether it is safe to keep making full power.
On some applications, the ECU does not read the MAT sensor directly. Instead, another controller measures manifold air temperature and sends it over the CAN (Controller Area Network) as a message. Either way, once the ECU sees the temperature cross its warning set point, it assumes the intake charge is too hot for safe, efficient combustion and starts protecting the engine.
This is not a sensor circuit failure like an open or short. FMI 16 specifically means the signal is valid but the reading is moderately high, meaning the ECU believes the actual air temperature really is too hot, not that the sensor or wiring is lying to it (though a bad sensor or wiring fault can still cause a false high reading).
What triggers a John Deere Engines SPN105FMI16 code?
The ECU sets this code when it senses manifold air temperature above its warning value set point. Cited thresholds vary by application: 88°C (190°F) for most applications, 90°C (194°F) on some OEM setups, and 100°C (212°F) on other OEM applications (with 120°C (248°F) for so-called T engines). The engine must be running for a minimum of 3 minutes before this DTC can become active on some platforms.
Common causes of SPN105FMI16
- Dirty, damaged, or poorly positioned terminals at the ECU 30-way connector or at the MAT sensor connector
- Open or short circuit in the wiring harness between the ECU and the MAT sensor, including the MAT input and ground circuits
- A bad or failing MAT sensor giving an inaccurate high-temperature reading
- Excessively high ambient air temperature pushing intake air temp near the limit under normal operation
- Restricted, dirty, or damaged charge air cooler, including internal plugging
- Loose cooling fan belt or a malfunctioning cooling fan reducing airflow across the charge air cooler
- Damaged cooling fan shroud allowing air to bypass the cooler core instead of pulling through it
- Restricted or damaged intake air piping limiting or disrupting airflow
- On some platforms: plugged air filter, exhaust leaks, boost leaks, EGR system leaks or flow sensor issues, VGT vane sticking or position sensor inaccuracy, air throttle restriction, or exhaust restriction
- Faulty ECU software (listed as a possible cause on some platforms)
How to troubleshoot John Deere Engines SPN105FMI16: first checks
- Do a visual and physical inspection of the ECU connector and MAT sensor connector first. Look for dirty, damaged, corroded, or poorly seated terminals before touching anything else.
- Check the charge air cooler for external blockage (bugs, debris, mud) and for internal plugging or damage. Also inspect the cooling fan shroud for damage that would let air bypass the cooler.
- Verify the cooling fan belt is tight and the fan itself is spinning and functioning correctly; a slipping belt or weak fan cuts charge air cooling fast.
- Inspect intake air piping from the filter to the intake manifold for restrictions, collapsed sections, or damage.
- Use a proper connector adapter test kit (JT07328 or equivalent) to check voltage and continuity in the MAT sensor circuit. Never force test probes directly into connector terminals, it can damage them and create a new fault.
- Check ambient conditions: if it's simply a very hot day and the machine is working hard, the derate may be the engine protecting itself as designed rather than a component failure.
- On applicable platforms, also rule out plugged air filters, boost leaks, exhaust leaks, and EGR or VGT-related airflow problems if the basic intake and cooling checks come back clean.
How the code clears
No separate clearing step is listed beyond fixing the root cause. Once manifold air temperature drops back below the warning maximum, the ECU increases power again, either back to full power or until temperature rises above the set point once more. There is no shutdown feature tied to this code; it works purely through the derate and recovery cycle described above.
Frequently asked questions
What does SPN 105 FMI 16 mean on a John Deere engine?
It means the ECU has detected manifold air temperature above its warning set point (commonly around 88°C (190°F), though the exact threshold varies by application). The engine will derate power until the temperature drops back down.
Will SPN 105 FMI 16 shut down my engine?
No. This code does not have a shutdown feature tied to it. Instead, the ECU derates the engine, commonly at 2% per minute down to 80% of full power, until the manifold air temperature falls back below the warning threshold.
Can hot weather alone trigger this code?
Yes. Excessively high ambient air temperature is listed as a direct possible cause. If the machine is working hard on a very hot day, the derate can be the ECU doing exactly what it's designed to do.
What part usually fails to cause this code?
There is no single part that always fails. Common culprits include a bad MAT sensor, corroded or damaged connector terminals, a restricted or dirty charge air cooler, a loose cooling fan belt, or a malfunctioning cooling fan. Wiring opens or shorts in the MAT sensor circuit are also possible.
Is SPN 105 FMI 16 related to SPN 1569 FMI 31?
Yes, when SPN 105 FMI 16 sets, SPN 1569 FMI 31 will also typically be present, since that code reflects the engine protection derate itself.
How long does the engine need to run before this code can become active?
On some platforms, the engine must run for a minimum of 3 minutes before this DTC can become active.
Should I keep driving or working with this code active?
You can continue operating since there's no shutdown feature, but expect reduced power from the derate. It's best to get the intake and cooling system inspected soon since running hot for extended periods stresses the engine even with the derate protection active.