John Deere Engines FMIT5 Fault Code: Analog Throttle (B) Input High
Analog Throttle (B) Input High · ai-assisted, editor-reviewed · Last updated 2026-07-21
TL;DR
FMIT5 sets on John Deere engines when the analog throttle (B) sensor signal voltage climbs above 4.7 volts, higher than the throttle lever can physically produce. The ECU will switch to another throttle input if one exists, or drop into a limp-home idle-only mode if the analog throttle (B) is the only throttle available or all throttles are faulted.
Medium severity. The engine keeps running, but you lose normal throttle control. If a backup throttle input exists the ECU switches to it and things may feel almost normal. If not, the engine is limited to idle speed only, which stops real work until it's fixed.
What does John Deere Engines error code FMIT5 mean?
The analog throttle (B) sensor is a potentiometer, a variable resistor that reports throttle lever position to the ECU as a voltage. Normal signal voltage runs between 1.0 volt and 4.0 volts, with about 1.0 volt at low idle and about 4.0 volts at high idle. The ECU can also learn slightly different low idle and high idle voltages for a given application.
FMIT5 means the ECU saw a voltage above 4.7 volts on the analog throttle (B) circuit, a value the throttle lever cannot produce through normal movement. That points to an electrical fault feeding extra voltage into the signal wire rather than an actual throttle position.
Because the sensor reading is now considered unreliable, the ECU stops trusting it. If a second throttle input is wired in, the ECU switches to that one automatically. If the analog throttle (B) is the only throttle, or every throttle input has also faulted, the ECU falls back to a default limp-home value that only allows idle speed.
What triggers a John Deere Engines FMIT5 code?
The code sets when the analog throttle (B) input voltage exceeds the sensor's high voltage specification of 4.7 volts, a level higher than what the throttle lever can physically reach.
Common causes of FMIT5
- Bad terminals or connector at the analog throttle (B) connector
- Bad terminals or connector at the ECU
- An open or short in the wiring harness between the sensor and ECU
- A bad analog throttle (B) sensor itself
- The idle stop on the throttle adjusted too low
- A bad ECU
How to troubleshoot John Deere Engines FMIT5: first checks
- Inspect the analog throttle (B) sensor connector and the ECU connectors for contamination, corrosion, damage, looseness, or poor seating.
- Check the wiring harness between the sensor and ECU for chafing or damage that could let the signal wire short to a power or reference voltage source.
- Wiggle-test connectors and harness while watching for the fault to change or disappear, since an intermittent high-voltage reading often points to a marginal connection rather than a dead sensor.
- Check the idle stop adjustment on the throttle lever, since John Deere lists this as a possible cause of the high voltage reading.
- With the connector disconnected, check the sensor itself for an internal fault that could push its output above the normal range.
- If the sensor and harness check out, consider the ECU connector and ECU itself as the remaining possible causes.
How the code clears
No separate clearing step or reset procedure is listed for this code. Once the underlying electrical fault, connector issue, or sensor problem is repaired and the voltage returns to the normal operating range, the code should stop being active. If more than one throttle input is used, verify normal throttle response returns after the repair since the ECU may have been running on a backup throttle input the whole time.
Frequently asked questions
What does John Deere FMIT5 mean?
It means the analog throttle (B) sensor signal voltage went above 4.7 volts, a level higher than the throttle lever can physically produce, so the ECU treats that throttle input as faulted.
Will the engine still run with FMIT5 active?
Yes, but throttle control changes. If another throttle input is available, the ECU switches to it. If the analog throttle (B) is the only throttle, or all throttle inputs are faulted, the ECU limits the engine to idle speed only using a default limp-home value.
What usually causes the throttle voltage to read too high?
John Deere lists bad terminals or connectors at either the sensor or the ECU, an open or short in the harness, a bad sensor, the idle stop adjusted too low, or a bad ECU.
How is FMIT5 different from FMIT6?
FMIT5 is analog throttle (B) input high, meaning the voltage read above the 4.7 volt ceiling. FMIT6 is the opposite: analog throttle (B) input low, meaning the voltage dropped too low, typically from an open circuit, a ground short, or lost sensor supply voltage. If your symptom is a low or missing signal rather than an impossibly high one, check the FMIT6 page instead.
Is this the same as the analog throttle (A) fault?
No. Analog throttle (A) has its own high and low codes, FMIT3 and FMIT4. FMIT5 and FMIT6 apply specifically to the analog throttle (B) circuit, a separate sensor input from throttle (A).
Can a bad idle stop adjustment really cause this code?
John Deere lists an idle stop adjusted too low as one of the possible causes, so yes, it is worth checking the mechanical idle stop setting on the throttle lever along with the electrical checks.
What should I check first before replacing the throttle sensor?
Start with a preliminary inspection of the ECU connectors and the analog throttle (B) sensor connector for contamination, damage, looseness, or poor positioning, then check the wiring for damage before assuming the sensor itself is bad.