John Deere Engines FMIT6 Fault Code: Analog Throttle (B) Input Low
Analog Throttle (B) Input Low · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
FMIT6 sets when the analog throttle (B) position sensor signal drops below 0.3 volts, a voltage lower than the throttle lever could physically produce. The ECU treats this as a wiring or sensor fault and either switches to another available throttle input or drops to a limp-home idle-only mode.
High severity. The engine will not respond normally to throttle commands once this code sets. If no backup throttle input exists, the machine is limited to idle speed only, which can strand equipment or interrupt work until repaired.
What does John Deere Engines error code FMIT6 mean?
The analog throttle (B) sensor is a potentiometer that tells the ECU where the throttle lever or pedal is positioned. Under normal operation, its voltage signal moves between roughly 1.0 volt at low idle and 4.0 volts at high idle. The ECU can even learn slightly different low and high idle voltages depending on the specific machine setup.
FMIT6 sets specifically when that signal voltage falls below 0.3 volts, a level the ECU knows cannot happen from normal throttle movement. That tells the control system the signal circuit itself has failed, whether from a short, an open wire, a bad connector, or a failed sensor, rather than the operator simply moving the throttle to an extreme position.
Once the code sets, the ECU reacts to protect engine control. If a second throttle input is wired into the system, the ECU ignores the faulted analog throttle (B) signal and runs off the other throttle. If there is no backup throttle, or if all throttle inputs are faulted, the ECU falls back to a default limp-home value that only allows idle speed, cutting off normal throttle response until the fault is fixed.
What triggers a John Deere Engines FMIT6 code?
The code sets when the analog throttle (B) input voltage drops below the sensor's low voltage specification, which for OEM applications is 0.3 volts. This is a voltage lower than what the throttle lever could physically produce at any position.
Common causes of FMIT6
- Bad terminals or connector at the analog throttle (B) connector
- Bad terminals or connector at the ECU
- Open or short circuit in the wiring harness between the sensor and ECU
- Bad analog throttle (B) sensor itself
- Idle stop on the throttle adjusted too low, which can push the mechanical range out of normal calibration
- Bad ECU
How to troubleshoot John Deere Engines FMIT6: first checks
- Visually inspect the ECU connectors for corrosion, moisture, bent pins, or loose terminals
- Inspect the analog throttle (B) sensor connector for contamination, damage, or poor seating
- Check the wiring harness between the throttle sensor and ECU for chafing, pinches, cuts, or shorts to ground
- Verify the throttle lever and idle stop mechanical adjustment is not set too low, which could affect sensor range
- With a meter, check throttle signal voltage at low and high idle positions to see if it stays within the expected 1.0 to 4.0 volt range or drops toward 0.3 volts or below
How the code clears
No separate clearing step is listed. Repair centers on finding and correcting the wiring, connector, sensor, or idle stop issue causing the low voltage condition. Once the underlying fault is corrected and the signal returns to a normal operating range, the code should stop being active. If the machine has more than one throttle input, confirm normal throttle response returns from the analog throttle (B) circuit itself, not just the backup, after repairs.
Frequently asked questions
What does FMIT6 mean on a John Deere engine?
It means the analog throttle (B) position sensor input voltage has dropped below 0.3 volts, a level lower than what the throttle lever could physically create. The ECU reads this as a fault in the sensor circuit rather than a real throttle position.
Will my engine still run with FMIT6 active?
Yes, but throttle response may be limited. If another throttle input is available, the ECU switches to it automatically. If not, the engine drops into a limp-home mode that only allows idle speed until the fault is fixed.
Can a bad idle stop adjustment cause FMIT6?
Yes. An idle stop adjusted too low is listed as a possible cause, since it can push the throttle sensor's mechanical range out of what the ECU expects.
What should I check first for FMIT6?
Start with a visual inspection of the ECU connectors and the analog throttle (B) sensor connector for contamination, damage, or poor positioning, then check the wiring harness for damage between the two.
Is FMIT6 caused by a bad sensor or bad wiring more often?
Both are listed as possible causes, along with bad terminals at either connector, an open or short in the harness, or a bad ECU. Careful voltage checks at the connector versus at the sensor help narrow down which one is at fault.
Does FMIT6 mean I need a new ECU?
Not necessarily. A bad ECU is listed as a possible cause, but it is one of several, and wiring, connector, and sensor issues are more common starting points before condemning the ECU.