John Deere Engines SPN3512FMI3 Fault Code: Sensor Supply #4 Voltage Out of Range High
Also called Engine Shutdown Commanded by Application
Sensor Supply #4 Voltage Out of Range High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 3512 FMI 3 sets when the John Deere ECU detects the 5-volt Sensor Supply #4 circuit reading above 5.26 volts. It is logged as a Warning-level code while the ignition is on and the fault is active, and it points to a short or wiring issue on the sensor supply feeding several optional components rather than one specific sensor.
Medium severity. This is logged by John Deere as a Warning-level alarm, not an immediate shutdown code, but it can affect throttle input and other sensor-fed functions since the ECU is working to hold proper operating conditions. Diagnose it before it leads to erratic engine behavior.
What does John Deere Engines error code SPN3512FMI3 mean?
SPN 3512 FMI 3 is a John Deere engine diagnostic trouble code tied to the ECU's internal 5-volt Sensor Supply #4 circuit. This circuit provides reference voltage to several sensors and switches, and the ECU constantly monitors it to make sure it stays within its designed range.
In this case, FMI 3 means the ECU has measured a voltage on that supply circuit above 5.26 volts, which is higher than it should read. Because several components can share this same supply circuit, the fault does not point to one single failed part. It means something on the shared circuit, in the wiring, at a connector, or inside the ECU itself, is letting the voltage climb too high.
John Deere lists this code under two closely related descriptions: 'Engine Shutdown Commanded by Application' and 'Sensor Supply #4 Voltage Out of Range High.' The alarm level given for this code is Warning, and the ECU's control unit response is simply to try to maintain proper operating conditions rather than force an immediate shutdown.
What triggers a John Deere Engines SPN3512FMI3 code?
The code is displayed when the ignition is on and the fault is active. The ECU detects a supply voltage greater than 5.26 volts on the Sensor Supply #4 circuit, which triggers the code.
Common causes of SPN3512FMI3
- A bad or shorted component using Sensor Supply #4 voltage: this can include the Primary Analog Throttle, an optional Fan Speed Sensor, an optional PTO Speed Sensor, an optional A/C High Pressure Switch, or an optional Isochronous/Droop Governor Switch.
- A short in the wiring harness feeding the Sensor Supply #4 circuit.
- Bad ECU software.
- A bad ECU.
- Bad terminals or a bad connector at the ECU.
- Bad terminals or a bad connector at one of the components listed above (Primary Analog Throttle, Fan Speed Sensor, PTO Speed Sensor, A/C High Pressure Switch, or Isochronous/Droop Governor Switch).
How to troubleshoot John Deere Engines SPN3512FMI3: first checks
- With the ignition on, check for an active SPN 3512 FMI 3 code and confirm it is currently active rather than a stored, inactive fault.
- Inspect the wiring harness for the Sensor Supply #4 circuit for chafing, pinched wire, or any place insulation could be worn through and causing a short.
- Check connectors and terminals at the ECU itself for corrosion, looseness, bent pins, or moisture intrusion.
- Check connectors and terminals at each component that uses Sensor Supply #4 voltage: the Primary Analog Throttle, and if equipped, the Fan Speed Sensor, PTO Speed Sensor, A/C High Pressure Switch, and Isochronous/Droop Governor Switch.
- Remember that other application-specific devices may also use this same sensor supply circuit; check the equipment's technical manual to identify every device tied to Sensor Supply #4 on that particular machine.
- If wiring and connectors check out, consider that the fault may be internal to the ECU, either a software issue or a hardware failure, and may require ECU-level diagnostics or reprogramming.
How the code clears
No separate clearing step is listed for this code. Since the alarm is tied to the ignition being on and the fault being currently active, correcting the underlying short or connection issue should allow the code to stop registering as active on its own. Always verify the fix by confirming the fault is no longer active after repairs are made.
Frequently asked questions
What does SPN 3512 FMI 3 mean on a John Deere engine?
It means the ECU has detected the Sensor Supply #4 voltage circuit reading above 5.26 volts, which is out of its normal range. This 5-volt supply feeds several optional sensors and switches, so the code points to a shared circuit problem rather than one specific part.
Is SPN 3512 FMI 3 a serious fault that will shut down my engine?
John Deere logs this as a Warning-level alarm. The ECU's response is to try to maintain proper operating conditions, not to force an immediate engine shutdown. Still, it should be diagnosed promptly since it can affect throttle and other sensor inputs.
Which components can cause this code?
Any component using Sensor Supply #4 voltage can be involved. That list includes the Primary Analog Throttle, and, where equipped, the Fan Speed Sensor, PTO Speed Sensor, A/C High Pressure Switch, and Isochronous/Droop Governor Switch. Other application-specific devices may also share this circuit, so check the machine's technical manual.
How do I know if the problem is the ECU or the wiring?
Start with the wiring and connectors: check for shorts in the harness and corroded or damaged terminals at both the ECU and the components using this supply. If everything checks out mechanically and electrically, the remaining possibilities are bad ECU software or a bad ECU itself.
When does the ECU display this code?
It is displayed when the ignition is on and the fault condition is currently active, meaning the ECU is seeing the out-of-range voltage in real time.
Is there a specific reset procedure for SPN 3512 FMI 3?
No reset procedure is listed for this code. Repairing the underlying short or connection issue should allow the fault to clear as active once the voltage returns to normal.