John Deere Engines SPN91FMI3 Fault Code: Primary Analog Throttle Signal Out of Range High
Also called Primary Analog Throttle Signal Out of Range Low, Primary Throttle Signal Out of Range High, Throttle #1 Signal Out of Range High, Throttle Voltage High
Primary Analog Throttle Signal Out of Range High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 91 FMI 3 means the ECU sees a primary analog throttle signal voltage that is higher than what the throttle sensor can physically produce. The engine responds by cutting throttle to 0% until the signal is valid again, and the recovery behavior depends on how the ECU is configured.
Medium severity. The engine will not stall outright, but throttle response drops to 0% and stays there until the fault clears and, depending on configuration, until the ignition is cycled. That means loss of operator control over engine speed, which matters most during active work or travel. Diagnose promptly rather than continuing to run the machine on a faulted throttle circuit.
What does John Deere Engines error code SPN91FMI3 mean?
SPN 91 FMI 3 is set when the primary analog throttle signal voltage arriving at the ECU corresponds to a throttle position that is greater than what is physically possible for the sensor. In plain terms, the ECU is being told the throttle is pushed further than the sensor can actually move, which tells the ECU something is wrong upstream of the signal itself rather than the operator's actual input.
This is a warning-level alarm code active whenever the ignition is on and the fault condition is present. It does not necessarily shut the engine down, but it does force the throttle to 0% until the ECU decides the signal is valid again.
Because the analog throttle circuit directly controls how much fuel the engine gets in response to operator demand, a faulted signal here removes normal throttle control. Depending on the recovery mode programmed into the ECU, getting throttle control back may require returning the pedal or lever to idle, waiting for the signal to clear, or cycling ECU power.
Common causes of SPN91FMI3
- Bad terminals, pins, or connector at the primary analog throttle sensor
- Open or shorted wiring in the harness between the throttle sensor and ECU
- Open in the return wire for the throttle sensor circuit
- Mispinned or incorrectly terminated harness connector
- Bad or failing primary analog throttle sensor itself
- Bad terminals, pins, or connector at the ECU
- Incorrect Trim configuration for the primary analog throttle within the ECU (on OEM applications)
- Bad ECU software
- Bad ECU
How to troubleshoot John Deere Engines SPN91FMI3: first checks
- Inspect the primary analog throttle sensor connector and terminals for corrosion, looseness, or physical damage before doing anything else
- Check the harness between the throttle sensor and ECU for chafing, pinches, or exposed wire that could cause a short to a high-voltage source
- Verify the return wire for the throttle circuit is intact and not open
- Confirm the ECU connector and pins are clean, seated, and undamaged
- On OEM-configured machines, check that the primary analog throttle Trim setting in the ECU matches the actual sensor installed
- Cycle the ignition after inspection to see if the fault clears and normal throttle control returns
How the code clears
No separate clearing step is listed beyond how the ECU's configured recovery mode works. With Idle Recovery, the default setting, the throttle must be returned to the low idle (0% throttle) position once the signal becomes valid again before normal operation resumes. With Resume Recovery, normal throttle operation resumes automatically as soon as the out-of-range condition clears, which can cause sudden engine speed changes if the fault is intermittent. With Locked Recovery, normal throttle operation only returns once the signal is valid again AND power has been cycled on the ECU.
Frequently asked questions
What does SPN 91 FMI 3 mean on a John Deere engine?
It means the ECU has detected a primary analog throttle signal voltage that is higher than what the throttle sensor can physically produce, so the signal is out of range high. The ECU responds by setting throttle to 0% until the condition clears.
Will my engine shut off when this code sets?
No, this is listed as a warning-level alarm. The engine keeps running, but throttle is forced to 0% until the signal becomes valid again, and getting normal throttle response back depends on the ECU's recovery mode.
Why won't my throttle respond after this fault clears?
If the ECU is set to Idle Recovery, the default mode, you must return the throttle to the low idle position (0% throttle) before normal operation resumes, even after the fault itself has cleared.
Why did my engine speed suddenly jump after this fault?
If the ECU is configured for Resume Recovery, normal throttle operation resumes automatically the instant the out-of-range condition clears. If the fault was intermittent, this can cause large, unexpected changes in engine speed.
Does cycling the key fix this code?
It depends on the recovery mode. Under Locked Recovery, normal throttle operation will not return until the signal is valid again AND ECU power has been cycled. Under Idle Recovery or Resume Recovery, cycling the key is not required by the logic itself, but it's still a reasonable step to try after inspecting the wiring.
Can a bad Trim setting cause this code on an OEM machine?
Yes. On OEM applications, the primary analog throttle is configured within the ECU on the Trim page. If that Trim configuration doesn't match the actual sensor, fault codes including this one can result.
What parts are most often responsible for SPN 91 FMI 3?
The most commonly listed causes are bad terminals or connectors at the throttle sensor or ECU, an open or shorted harness, a bad return wire, a mispinned connector, a failed throttle sensor, or in some cases bad ECU software or a bad ECU itself.