John Deere Engines SPN105 Fault Code: Manifold Air Temperature Signal Extremely High
Also called Derated Torque Curve Selected, Intake Manifold Air Temperature Signal Extremely High, Manifold Air Temperature Extremely High
Manifold Air Temperature Signal Extremely High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 105 FMI 0 means the ECU has either seen manifold (charge) air temperature go extremely high or seen the torque curve select input pulled to ground. Either way the engine responds by cutting power through a derate, and in some cases will shut down. Treat it as an overheating intake air problem until you prove otherwise.
High severity. The ECU responds to this code with an automatic power derate, and on some configurations a shutdown after a short delay. Continued operation at high manifold air temperature risks engine damage, so this should be diagnosed before returning to full duty.
What does John Deere Engines error code SPN105 mean?
SPN 105 FMI 0 covers two related conditions in John Deere engine ECUs. The first is a torque curve select input that has been pulled to ground, which on OEM applications is normally done on purpose by a charge air temperature switch when charge air temperature gets too hot. The second is the manifold air temperature (MAT) sensor itself reporting a temperature above the ECU's threshold.
The MAT sensor is a thermistor mounted in the intake manifold. Its resistance changes with temperature, which changes the voltage the ECU sees: hotter air gives a lower signal voltage, cooler air gives a higher one. When the ECU interprets that signal as an extremely high temperature, or when the torque curve select circuit is shorted to ground, engine protection logic kicks in.
In practice this code is the engine telling you the intake charge air is running too hot for safe operation, whether that heat is real (cooling or airflow problem) or the signal path is faulty (sensor, wiring, or connector fault).
What triggers a John Deere Engines SPN105 code?
On air-to-air aftercooled (H) engine OEM applications, the code can set when charge air temperature exceeds 94°C (201°F). On the MAT sensor side, it sets when the ECU senses manifold air temperature above 100°C (212°F) on H engines, or above 120°C (248°F) on T engines, for OEM applications. The engine must be running for a minimum of three minutes before the DTC can go active. Other applications may use different thresholds listed in application-specific specifications.
Common causes of SPN105
- Excessively high ambient air temperature
- Restricted, dirty, or damaged charge air cooler, including internal plugging
- Loose or worn cooling fan belt
- Malfunctioning cooling fan or damaged fan shroud
- Restricted or damaged intake air piping
- Faulty derated torque curve wiring, including a short to ground on that circuit
- Bad terminals or connector at the ECU or at the manifold air temperature sensor
- Open or short in the circuit to the manifold air temperature sensor
- Bad manifold air temperature sensor
- Plugged or dirty air filter
- Exhaust leak, boost leak, or EGR system leak
- Loose or broken EGR flow sensor venturi bracket
- VGT vanes sticking or VGT vane position sensor reading inaccurately
- Air throttle restriction, exhaust restriction, or damaged turbocharger
- Bad ECU software or a bad ECU
How to troubleshoot John Deere Engines SPN105: first checks
- Connect a diagnostic tool (DST or SERVICE ADVISOR) and read all active and stored DTCs first, since related codes may point to the actual root cause.
- Visually inspect the charge air cooler for external plugging, dirt, or damage, and check that airflow through it is not blocked.
- Check the cooling fan belt for looseness, and confirm the cooling fan and fan shroud are intact and operating correctly.
- Inspect intake air piping and the air filter for restriction, damage, or leaks, and check boost and EGR connections for leaks.
- Inspect the manifold air temperature sensor connector and terminals for corrosion, damage, or looseness. Use a proper connector adapter test kit rather than probing terminals directly to avoid damaging them.
- Check the derated torque curve wiring for an unintended short to ground.
- If wiring and cooling components check out, test the manifold air temperature sensor itself against its known good resistance/voltage behavior.
How the code clears
No separate clearing step is listed beyond fixing the root cause. Once the actual problem, whether it is a cooling restriction, wiring fault, or bad sensor, is corrected and manifold air temperature returns to normal, the derate should come out of effect. With the shutdown feature enabled, engine shutdown occurs about 30 seconds after the code sets, so the engine will need to be restarted once the issue is addressed. Confirm with a diagnostic tool that the code is no longer active after repairs.
Frequently asked questions
What does SPN 105 FMI 0 mean on a John Deere engine?
It means the ECU has detected either an extremely high manifold air temperature signal or a torque curve select input pulled to ground. Both point to the engine's charge air running too hot or a wiring fault making it look that way, and both cause the ECU to reduce engine power.
Will SPN 105 FMI 0 shut my engine down?
It can. Depending on configuration, the ECU either derates the engine gradually or, on units with the shutdown feature enabled, shuts the engine down about 30 seconds after the code becomes active. Either way, expect a significant loss of power first.
How much power do I lose with this code active?
It depends on which fault path triggered it. Some configurations derate the engine 20% per minute until it reaches 60% of full power, while others derate as fast as 60% per minute to the same 60% floor. In all cases, expect a serious power reduction, not a minor one.
Can a dirty air filter or clogged charge air cooler cause this code?
Yes. A plugged air filter, an externally or internally plugged charge air cooler, restricted intake piping, or a damaged fan shroud are all listed causes that let manifold air temperature climb too high.
Is this code caused by a bad sensor or a real overheating problem?
It can be either. The manifold air temperature sensor, its wiring, or its connector can fail and send a false high reading, or the intake air genuinely can be overheating due to a cooling or airflow restriction. Both need to be checked.
How long does the engine need to run before this code can set?
The engine must run for a minimum of three minutes before this DTC can become active, according to the manufacturer's diagnostic logic.
Is it safe to keep driving or working with SPN 105 FMI 0 active?
Not for long. Since the ECU is already cutting power and may shut the engine down, plan to stop and diagnose the cause as soon as it's safe to do so rather than continuing to push the engine under derate.