John Deere Engines SPN654FMI6 Fault Code: Injector #4 Circuit Has Low Resistance
Also called Cylinder #4 EI Circuit Shorted, Cylinder #4 EUI Circuit Shorted, Electronic Unit Pump #4 Circuit Has Low Resistance, Injector #1 Circuit Has Low Resistance, Injector #4 Spill Valve Circuit Has Low Resistance
Injector #4 Circuit Has Low Resistance · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 654 FMI 6 means the ECU has detected a short or low resistance in the cylinder #4 fuel injection circuit, whether that's an electronic unit injector (EUI), electronic injector (EI), or unit pump depending on engine family. Cylinder #4 will not fire when this code is active, causing a rough-running or misfiring engine. The ECU keeps trying to control the engine normally, but power and smoothness will suffer.
Medium severity. This code carries a Warning alarm level on the systems that specify one, and the ECU continues attempting normal engine control. It is not an immediate shutdown condition, but a dead or misfiring cylinder #4 will hurt performance, fuel economy, and can lead to further engine stress if ignored, so it should be diagnosed the same shift it appears.
What does John Deere Engines error code SPN654FMI6 mean?
This code applies to the cylinder #4 fuel delivery circuit, but the exact hardware differs by engine. On 10.5 L and 12.5 L engines, fuel is delivered by electronic unit injectors (EUIs), which combine the injection pump and injector in one unit mounted in the cylinder head. On the 8.1 L engine, electronic injectors (EIs) draw high pressure fuel from a common rail and are switched by a Two-Way Valve (TWV). Other engine families in this ECU family use a separate electronic unit pump for each cylinder instead of a combined EUI.
In all these designs, the ECU supplies a shared high voltage or common power wire to a bank of cylinders (1, 2, 3 on one wire; 4, 5, 6 on another) and controls each individual injector or pump by switching its own ground (low side) circuit on and off. SPN 654 FMI 6 means the ECU has found a short or abnormally low resistance specifically in the cylinder #4 low-side circuit, whether that's the injector solenoid, the EUI spill valve solenoid, or the unit pump coil.
When the fault is active, cylinder #4 will not fire. On the unit pump version, this DTC is specifically not caused by a short to ground of the unit pump circuit itself, it points instead to internally shorted coil windings in the pump or injector, or a wire-to-wire short between two low-side circuits. A wire-to-wire short between two injector or pump circuits will typically set two active low-resistance codes at once, one for each affected cylinder.
What triggers a John Deere Engines SPN654FMI6 code?
The engine must be cranking or running with the error condition active for the ECU to display this code. It can also appear during a Harness Diagnostic Mode Test in Service ADVISOR. On electronic injector (EI/common rail) systems, the code will also display during that harness test only if fuel rail pressure is below 5 MPa (725 psi).
Common causes of SPN654FMI6
- Bad terminals or connector at the ECU
- Bad terminals or connector at the EUI, EI, or unit pump harness connector (location varies: back of cylinder head for EUI, side of cylinder head for EI)
- Bad terminals or connector at connector C01 (unit pump systems) or at the #4 injector connection directly
- A bad #4 EUI, EI solenoid, unit pump, or injector with internally shorted coil windings
- An open or short in the harness between the ECU and the injector/EUI/unit pump, including the main engine harness
- An open or short specifically in the 90V circuit (EI systems)
- A wire-to-wire short between the low-side wiring of two different injector or unit pump circuits, which will show up as low-resistance codes on both affected cylinders at once
- Bad ECU software
- A bad ECU
How to troubleshoot John Deere Engines SPN654FMI6: first checks
- Visually inspect the 48-way ECU connector and all connectors between the ECU and the injector or unit pump harness for dirty, damaged, corroded, or poorly seated terminals
- Inspect the injector/EUI harness connector at the cylinder head (rear on EUI engines, side on EI engines) for contamination, damage, or poor positioning
- Check the wiring harness between the ECU and cylinder #4 for chafing, pinched insulation, or exposed conductors that could cause a short, including the main engine harness and, on EI engines, the 90V circuit
- On unit pump systems, check connector C01 and the terminals at unit pump #4 specifically
- Look for any wiring routing where two injector or unit pump low-side wires run close together or share a connector cavity, since a wire-to-wire short between two circuits can set this code on more than one cylinder simultaneously
- Run a Harness Diagnostic Mode Test in Service ADVISOR if available; on EI engines confirm fuel rail pressure is below 5 MPa (725 psi) before expecting the test to display the DTC accurately
How the code clears
No separate clearing step is listed. The ECU continues attempting to control the engine normally while the fault is active, and the code should clear once the underlying short or low-resistance condition at cylinder #4 is repaired and verified with a rerun of the diagnostic or harness test.
Frequently asked questions
What does SPN 654 FMI 6 mean on a John Deere engine?
It means the ECU has detected a short or abnormally low resistance in the cylinder #4 fuel injection circuit. Depending on the engine, this is the electronic unit injector (EUI), electronic injector (EI), or electronic unit pump circuit for cylinder #4.
Will my engine run with this code active?
Yes, but not well. Cylinder #4 will not fire while the fault is active, so expect a rough idle, misfire, loss of power, and possibly increased fuel consumption. The ECU will keep trying to control the engine in a normal manner, it just cannot fire that cylinder.
Is SPN 654 FMI 6 a shutdown code?
No shutdown is listed. On the systems that specify an alarm level, it is listed as a Warning, not a shutdown or derate. Even so, a dead cylinder should be diagnosed promptly rather than run indefinitely.
Can a wiring problem on another cylinder cause this code?
Yes. A wire-to-wire short between the low-side wiring of two different injector or unit pump circuits can cause active low-resistance codes on both affected cylinders at the same time, not just cylinder #4. If you see this code alongside a similar code on another cylinder, check for shared or adjacent wiring runs.
Does this mean I need a new injector or unit pump?
Possibly, but not necessarily. The list of possible causes includes bad terminals or connectors at the ECU or harness connector, an open or short in the harness itself, bad ECU software, or a bad ECU, in addition to a bad injector, EUI, or unit pump. Start with the connectors and wiring before replacing the injector or pump.
Where do I start diagnosing this code?
Start with a visual inspection of the ECU connector and the injector or EUI harness connector at the cylinder head, looking for dirty, damaged, or poorly seated terminals. Then check the wiring between the ECU and cylinder #4 for damage before condemning the injector, EUI, or unit pump.
Is this the same fault on every John Deere engine?
The underlying meaning is the same, a short or low resistance in the cylinder #4 injection circuit, but the hardware differs. 10.5 L and 12.5 L engines use EUIs, the 8.1 L engine uses EIs fed from a common rail, and other engines in this family use individual electronic unit pumps, so the exact wiring and connector locations vary by engine.