John Deere Engines SPN1069FMI31 Fault Code: Calculated Tire Size Is Out Of Range
Also called Tire Size Error, Tire Size Invalid
Calculated Tire Size Is Out Of Range · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 1069 FMI 31 means the ECU has determined that the programmed or CAN-supplied tire size value is incorrect. Also seen as DTC 1069.31 or DTC 001069.31. The ECU defaults to assuming the largest tire size and will limit engine speed or road speed until the tire size is reprogrammed correctly.
Medium severity. This code does not indicate a mechanical failure, but it does cause the ECU to assume the largest tire size and impose speed limits, which affects drivability and can mask real speed/performance issues. Diagnose within the shift rather than continuing to run with a bad tire size value.
What does John Deere Engines error code SPN1069FMI31 mean?
This fault is about data, not hardware damage. The engine ECU relies on a tire size value, either programmed directly into it or sent over the CAN bus from another controller (such as a Reverser Control Unit), to correctly calculate vehicle road speed and manage engine speed limiting in top gear. When the ECU checks that tire size value and finds it doesn't make sense, it sets SPN 1069 FMI 31.
Once the code sets, the ECU falls back to a safe default: it assumes the largest tire size is fitted. This is a protective measure, but it changes vehicle behavior. Depending on the platform, the ECU will limit engine speed to 1950 rpm or 1912 rpm when the vehicle is in top gear, and road speed limiting may kick in at a speed lower than what is actually specified for that machine.
In short, this code will not strand you, but it will change how the machine drives and shifts, and it needs to be corrected through a calibration procedure rather than a parts repair.
Common causes of SPN1069FMI31
- Tire size was not programmed correctly into the ECU during setup or after a component change.
- Tire size value programmed into the ECU does not match the actual tire size on the vehicle, or is out of the valid range the ECU expects.
- On platforms using CAN-supplied tire size, the value received over the CAN bus from the Reverser Control Unit (RCU) is incorrect based on what is programmed into the ECU.
- ECU tire size calibration needs to be redone, even if connectors at the ECU, BIF, and BCU all check out electrically fine.
How to troubleshoot John Deere Engines SPN1069FMI31: first checks
- Confirm the actual tire size fitted to the vehicle so you know what value should be programmed.
- Check that the connectors at the ECU, BIF (if equipped), and BCU are clean, seated, and free of corrosion, since a tire size error can occur even when these connectors are electrically fine.
- Verify whether the tire size is programmed locally into the ECU or supplied over CAN from the Reverser Control Unit, since the correction path differs.
- Look for any recent tire changes, component swaps, or ECU replacements that could have reset or invalidated the tire size setting.
How the code clears
Reprogram the tire size using the tire size calibration program on the vehicle. This is the specified fix for this code; no separate reset procedure is listed beyond performing this calibration. For the exact calibration steps, refer to the application technical manual for your machine.
Frequently asked questions
What does SPN 1069 FMI 31 mean on a John Deere engine?
It means the ECU has checked the tire size value, either programmed directly or received over CAN, and found it to be incorrect or out of range. The ECU responds by assuming the largest tire size and limiting engine or road speed.
Will this code stop my machine from running?
No. The engine will keep running, but the ECU defaults to assuming the largest tire size, which triggers speed limiting. In top gear, engine speed may be capped at 1950 rpm or 1912 rpm depending on the platform, and road speed limiting may occur below the specified speed.
How do I fix SPN 1069 FMI 31?
Reprogram the tire size using the tire size calibration program on the vehicle, entering the correct value for the tires actually fitted. This is the documented fix for the code.
I checked the ECU, BIF, and BCU connectors and they're fine, why is the code still there?
Even with good connectors, the tire size can still be programmed incorrectly. The fix is recalibrating the tire size value in the ECU, not repairing wiring or connectors.
Does this code affect top speed or shifting?
Yes. Once set, the ECU assumes the largest tire size, which can cause road speed limiting to occur at a speed lower than the vehicle's actual specified speed, and it limits engine speed in top gear.
Is this the same as DTC 1069.31?
Yes, DTC 1069.31 and DTC 001069.31 are alternate ways some displays and service tools show SPN 1069 FMI 31. They describe the same tire size error condition.
Where does the ECU get the tire size information from?
On some platforms it's programmed directly into the ECU. On others, it's sent to the ECU over the CAN bus by another controller, such as the Reverser Control Unit (RCU), regarding tire size and throttle position information.