John Deere Engines SPN653FMI6 Fault Code: Injector #3 Circuit Has Low Resistance
Also called Cylinder #3 EI Circuit Shorted, Cylinder #3 EUI Circuit Shorted, Electronic Unit Pump #3 Circuit Has Low Resistance, Injector #2 Circuit Has Low Resistance, Injector #3 Spill Valve Circuit Has Low Resistance
Injector #3 Circuit Has Low Resistance · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 653 FMI 6 means the ECU has detected a short or low resistance condition in the cylinder #3 fuel injection circuit, whether that's an EUI (electronic unit injector), EI (electronic injector), or electronic unit pump depending on your engine. Cylinder #3 will not fire while this fault is active, causing a rough-running or misfiring engine. The ECU will keep trying to control the engine normally, but performance and emissions will suffer until it's fixed.
Medium severity. This code is logged as a Warning-level alarm on the electronic injector/unit pump variants, and the ECU keeps attempting normal engine control. However, cylinder #3 not firing means real performance loss, rough idle, and possible long-term damage from unbalanced cylinder loading if ignored. Diagnose within the shift rather than continuing to run the machine hard.
What does John Deere Engines error code SPN653FMI6 mean?
SPN 653 FMI 6 covers several closely related fuel system designs across John Deere engines. On 10.5 L and 12.5 L engines with electronic unit injectors (EUIs), each injector combines the injection pump and injector in one unit mounted in the cylinder head, spraying directly into the cylinder. The ECU fires each injector by opening and closing its ground-side circuit while power is shared among cylinders 1-3 on one wire and 4-6 on another.
On 8.1 L engines with electronic injectors (EIs), a two-way valve inside each injector controls a spill valve fed from a high pressure common rail. Other engine families use an electronic unit pump per cylinder or an injector circuit with a shared high-voltage supply switched at the low (ground) side by the ECU.
In every version, FMI 6 means the ECU has found a short or abnormally low resistance in the cylinder #3 circuit. This can be an internal short in the injector or unit pump's coil windings, or a wire-to-wire short between two cylinders' low-side wiring. Because the ECU can't safely energize a shorted circuit, it disables firing on cylinder #3 to avoid further damage.
Common causes of SPN653FMI6
- Bad terminals or connector at the ECU
- Bad terminals or connector at the EUI, EI, or injector/unit pump harness connector (including the 12-way connector on 6.8L engines or 6-way connector on 4.5L engines, or connector C01 on unit pump systems)
- A bad #3 injector, EUI, EI, or unit pump with low internal coil resistance from shorted windings
- Open or short in the harness between the ECU and the injector or unit pump connector, including the 90V circuit on EI-equipped 8.1L engines
- A wire-to-wire short between the low-side ground wiring of two injectors or unit pumps, which will set active low-resistance codes on both cylinders at once
- Bad injector, EUI, or unit pump wiring harness
- Bad ECU software
- Bad ECU
How to troubleshoot John Deere Engines SPN653FMI6: first checks
- Inspect the ECU connector (including the 48-way connector on EUI-equipped engines) for dirty, damaged, corroded, or poorly seated terminals
- Inspect the injector, EUI, EI, or unit pump harness connector at the cylinder head, at the back of the head on EUI engines or the side of the head on EI engines, for contamination, damage, or poor positioning
- Check all wiring and connectors between the ECU and the cylinder #3 circuit for chafing, pinched wire, or shorts, paying attention to any point where two cylinders' low-side wires run close together
- Use Service ADVISOR's Harness Diagnostic Mode Test to help isolate the fault; on injector-equipped engines this test may only display accurately when fuel rail pressure is below 5 MPa (725 psi)
- Check resistance of the #3 injector, EUI, EI, or unit pump itself to rule out internally shorted coil windings
- Rule out a wire-to-wire short by checking whether a second cylinder also shows an active low-resistance code at the same time
How the code clears
No separate clearing step is listed. Repair the underlying wiring, connector, or component issue, then verify the code does not return during cranking or running and, if available, during a Harness Diagnostic Mode Test in Service ADVISOR.
Frequently asked questions
What does SPN 653 FMI 6 mean on a John Deere engine?
It means the ECU has detected a short or low resistance condition in the cylinder #3 fuel injection circuit. Depending on your engine family this circuit may be an electronic unit injector (EUI), electronic injector (EI), or electronic unit pump.
Will my engine run with this code active?
Yes, but not well. Cylinder #3 will not fire while the code is active, and the ECU will keep trying to control the engine in a normal manner around that missing cylinder. Expect rough running, reduced power, and possible rough idle.
Can a bad connector cause this code instead of a bad injector?
Yes. Dirty, damaged, or poorly seated terminals at the ECU connector or at the injector/unit pump harness connector are listed as common causes, so a thorough visual and physical inspection of connectors should come before replacing components.
Does this code mean cylinder #3's injector is definitely bad?
Not necessarily. This code can also be caused by a wire-to-wire short between the low-side wiring of two injectors or unit pumps, which will set active low-resistance codes on both affected cylinders at once. Always check for a second active code before condemning the injector.
Is SPN 653 FMI 6 an emergency shutdown code?
No, it's logged as a Warning-level alarm on several variants, and the ECU attempts to keep the engine running normally. That said, running on five out of six cylinders for an extended period isn't good for the engine, so it should be diagnosed promptly.
What's the difference between this code on EUI, EI, and unit pump engines?
The underlying hardware differs (EUIs combine pump and injector in one unit, EIs use a two-way valve fed by a common rail, and unit pumps are separate pumps), but in all cases the ECU is detecting a short or low resistance in the cylinder #3 circuit's ground-side control.
Where is the injector or EUI connector located for inspection?
On EUI-equipped 10.5 L and 12.5 L engines, the harness connector is at the back of the cylinder head. On EI-equipped 8.1 L engines, it's at the side of the cylinder head. Always check the ECU connector as well, including the 48-way ECU connector on EUI engines.