John Deere Engines SPN652FMI6 Fault Code: Injector #2 Circuit Has Low Resistance
Also called Cylinder #2 EI Circuit Shorted, Cylinder #2 EUI Circuit Shorted, Electronic Unit Pump #2 Circuit Has Low Resistance, Injector #2 Spill Valve Circuit Has Low Resistance, Injector #3 Circuit Has Low Resistance
Injector #2 Circuit Has Low Resistance · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 652 FMI 6 means the ECU has detected low resistance or a short in the cylinder #2 fuel injection circuit, which covers electronic unit injectors (EUI), electronic injectors (EI), or unit pumps depending on engine. Cylinder #2 will not fire correctly when this code is active. Alarm level is listed as Warning, and the ECU will keep trying to control the engine normally.
Medium severity. The code is flagged as a Warning level alarm and the ECU continues attempting normal engine control, so the engine will typically keep running. However, with cylinder #2 not firing, expect rough running, power loss, and possible long-term wear if left unaddressed. Diagnose within the shift rather than ignoring it.
What does John Deere Engines error code SPN652FMI6 mean?
SPN 652 FMI 6 is set when the ECU detects low resistance or a short somewhere in the cylinder #2 fuel delivery circuit. Depending on the engine platform, this circuit could be an electronic unit injector (EUI) on 10.5 L and 12.5 L engines, an electronic injector (EI) on the 8.1 L engine, an electronic unit pump, or an electronic injector on smaller displacement engines (6.8L or 4.5L).
In EUI and EI systems, the ECU controls fuel delivery by switching a solenoid or Two-Way Valve (TWV) on and off, which opens and closes a spill valve inside the injector. Power to injectors is shared across cylinders 1, 2, and 3 on one common wire, and cylinders 4, 5, and 6 on another. The ECU switches the low side (ground) of each individual injector circuit to fire it.
When this code sets, cylinder #2 will not fire. This is not the same as a short to ground of the circuit. It's specifically a low resistance condition, which can come from shorted internal coil windings inside the injector or unit pump itself, or from a wire-to-wire short between the low side wiring of two injectors. If that's the cause, expect to see this code active alongside a matching low resistance code on the other affected cylinder.
Common causes of SPN652FMI6
- Bad terminals or connector at the ECU
- Bad terminals or connector at the EUI, EI, or injector harness connector (location varies: back of cylinder head for EUI, side of cylinder head for EI, or the 12-way/6-way connector on 6.8L/4.5L engines)
- Bad #2 injector, EUI, EI solenoid, or unit pump itself
- Bad injector or unit pump wiring harness
- Open or short in the harness between the ECU and the injector or unit pump connector
- Open or short in the 90V circuit (8.1L engine EI systems)
- Bad ECU or bad ECU software
- Wire-to-wire short between the low side wiring of two injectors or unit pumps, which will show up as low resistance codes on both affected cylinders at once
How to troubleshoot John Deere Engines SPN652FMI6: first checks
- Perform a visual inspection of the 48-way ECU connector and all connectors between the ECU and the cylinder #2 injector or unit pump harness connector. Look for dirty, damaged, corroded, or poorly seated terminals.
- Inspect the injector or EUI/EI harness connector at the cylinder head (location depends on engine: back of the cylinder head for EUI, side of the cylinder head for EI) for contamination, damage, or poor positioning.
- Check the wiring harness for chafing, pinched sections, or damage anywhere between the ECU and the cylinder #2 circuit, including checking for a wire-to-wire short with the adjacent injector circuits.
- If another cylinder is also showing a low resistance code at the same time, treat that as a strong sign of a wire-to-wire short between the two circuits rather than two separate failed injectors.
- Run a Harness Diagnostic Mode Test in Service ADVISOR if available. Note that on some engines this test only displays the DTC properly when fuel rail pressure is below 5 MPa (725 psi).
- Check resistance of the #2 injector, EUI, or unit pump coil itself if wiring and connectors check out, since shorted internal coil windings are a listed cause.
How the code clears
No separate clearing step is listed. Repair procedures center on inspecting and correcting the terminals, connectors, harness, or injector/unit pump causing the low resistance or short, then verifying the code does not return once the engine is run again. No reset procedure is listed for this code beyond fixing the underlying fault.
Frequently asked questions
What does SPN 652 FMI 6 mean on a John Deere engine?
It means the ECU has detected low resistance or a short in the cylinder #2 fuel injection circuit. Depending on your engine, this circuit is the electronic unit injector (EUI), electronic injector (EI), or electronic unit pump for cylinder #2. Cylinder #2 will not fire while this code is active.
Is it safe to keep driving or running the engine with this code active?
The alarm level is listed as Warning, and the ECU will attempt to control the engine in a normal manner. That means the engine will likely keep running, but with cylinder #2 not firing you can expect rough running and reduced power. It's best to diagnose the cause within your shift rather than running it long term.
Why would cylinder #2 and another cylinder both show a low resistance injector code at the same time?
This is a known pattern with this fault. A wire-to-wire short between the low side wiring of two injector or unit pump circuits will cause active low resistance codes on both cylinders simultaneously. If you see paired codes, focus your search on where the two circuits' wiring runs together.
Is this the same as a short to ground in the unit pump circuit?
No. For the electronic unit pump version of this fault, it's specifically stated that this DTC is not caused by a short to ground of the unit pump circuit. It's caused by low coil resistance internally in the pump or a wire-to-wire short between two pump circuits.
Where do I start looking for the fault?
Start with a visual inspection of the ECU connector (48-way on EUI systems) and the injector or unit pump harness connector at the cylinder head. Look for dirty, damaged, or poorly positioned terminals before moving on to wiring and component-level checks.
Can a bad ECU cause this code?
Yes, a bad ECU or bad ECU software is listed among the possible causes across all engine variants, but it's typically one of the last things to suspect after ruling out connectors, harness, and the injector or unit pump itself.
What's the difference between EUI, EI, and unit pump systems for this code?
EUI (electronic unit injector) systems are used on 10.5 L and 12.5 L engines and combine the injection pump and injector in one unit. EI (electronic injector) systems on the 8.1 L engine use a Two-Way Valve and a high pressure common rail. Electronic unit pump systems use a separate pump per cylinder with a shared high voltage supply and individual ground switching. The fault logic and wiring concept behind SPN 652 FMI 6 is similar across all three, just with different component names and connector locations.