John Deere Engines SPN655FMI5 Fault Code: Injector #5 Circuit Has High Resistance
Also called Cylinder #5 EI Circuit Open, Cylinder #5 EUI Circuit Open, Electronic Unit Pump #5 Circuit Has High Resistance, Injector #5 Spill Valve Circuit Has High Resistance
Injector #5 Circuit Has High Resistance · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 655 FMI 5 means the ECU has detected an open or high-resistance condition in the cylinder #5 injector circuit, whether that's an EUI, EI, or common-rail electronic injector depending on engine. When it sets, cylinder #5 will not fire or may run with reduced injector performance, and the engine will otherwise keep running in a degraded state.
Medium severity. The engine keeps running since the ECU attempts to control it normally, but one cylinder not firing (or firing poorly) causes rough running, power loss, and possible long-term wear from unbalanced cylinder loads. Diagnose within the shift rather than ignore it.
What does John Deere Engines error code SPN655FMI5 mean?
SPN 655 FMI 5 points to the fuel injection circuit for cylinder #5. On 10.5 L and 12.5 L engines, this circuit feeds an electronic unit injector (EUI), a combination injection pump and injector built into the cylinder head that sprays directly into the cylinder. On 8.1 L engines it's an electronic injector (EI) fed by a high pressure common rail, using a Two-Way Valve (TWV) to open and close the spill valve. Other engine families use a similar high-side/low-side electronic injector circuit.
In all versions, the ECU supplies a shared power feed to a bank of injectors (cylinders 1-3 share one wire, 4-6 share another), then switches the ground side for each individual injector to fire it. FMI 5 specifically means the ECU is reading an open circuit, or in some versions, a few extra ohms of resistance somewhere in the cylinder #5 injector wiring, connector, or the injector itself.
When this code is active, cylinder #5 either will not fire at all (open circuit versions) or the ECU will keep trying to control the engine normally despite the added resistance (high-resistance versions). Either way, expect a rough-running or underpowered engine until it's fixed.
What triggers a John Deere Engines SPN655FMI5 code?
The ECU sets this code when it detects an open circuit, or in high-resistance versions, additional series resistance of a few ohms, anywhere in the cylinder #5 injector circuit while the engine is cranking or running. On engines using Service ADVISOR's Harness Diagnostic Mode Test, the code can also display during that test provided fuel rail pressure is below 5 MPa (725 psi).
Common causes of SPN655FMI5
- Bad terminals or connector at the ECU (48-way connector on EUI engines, or other ECU connector points)
- Bad terminals or connector at the injector/EUI/EI harness connector, including the 12-way (6.8L) or 6-way (4.5L) connector on affected engines
- Open or short in the wiring harness between the ECU and the injector, including the main harness or the 90V circuit on EI engines
- Bad injector: faulty #5 EUI, #5 EI solenoid, or #5 electronic injector itself
- Bad injector wiring harness or bad EUI harness located in the cylinder head
- Bad ECU software
- Bad ECU
How to troubleshoot John Deere Engines SPN655FMI5: first checks
- Perform a visual inspection of the ECU connector, the injector/EUI harness connector at the cylinder head, and any connectors in between for dirt, corrosion, damage, or poorly seated terminals
- Check the injector harness wiring for chafing, pinches, or damage along its full run between the ECU and cylinder #5
- Look closely at the shared power feed wire for cylinders 4, 5, and 6, since an open in this common supply can trigger high-resistance codes on multiple injector circuits at once, not just cylinder #5
- Inspect the #5 injector connector itself for corrosion or a poor connection, and reseat or clean terminals as needed
- If wiring and connectors check out, test the #5 injector and its harness for continuity and resistance to isolate whether the fault is in the injector, the harness, or the ECU
How the code clears
No separate clearing step is listed. Once the open circuit or high-resistance condition in the cylinder #5 injector circuit is repaired, the code should stop being active on the next key cycle or engine run. On engines with a documented troubleshooting sequence, check SPN 627 FMI 1 as part of the same diagnostic path before finishing repairs.
Frequently asked questions
What does SPN 655 FMI 5 mean on a John Deere engine?
It means the ECU has detected either an open circuit or, on some engines, high resistance in the wiring or connector for the cylinder #5 fuel injector. Depending on the engine family, this circuit controls an electronic unit injector (EUI), an electronic injector (EI), or a common-rail electronic injector.
Will the engine still run with SPN 655 FMI 5 active?
Yes, but not normally. On open-circuit versions of this code, cylinder #5 will not fire at all. On high-resistance versions, the ECU tries to control the engine normally despite the fault, which can still cause rough running or reduced power.
What usually causes this code?
Most cases trace back to bad terminals or connectors at the ECU or at the injector harness connector, an open or short somewhere in the wiring harness, or a failed injector. A bad ECU is possible but less common and should be the last thing checked.
Where should I start looking first?
Start with a visual inspection of the ECU connector and the injector harness connector at the cylinder head. Look for dirty, damaged, or poorly seated terminals before you start pulling wiring apart or condemning the injector.
Can one bad wire cause problems on more than just cylinder #5?
Yes. Since cylinders 4, 5, and 6 share a common power feed wire on some engines, an open circuit in that shared supply can trigger high-resistance codes on multiple injector circuits at the same time, not just cylinder #5.
Is there a specific reset procedure for this code?
No reset procedure is listed for this code. Once the underlying open circuit or high-resistance issue is repaired, the code should clear on its own during normal engine operation.
Does fuel rail pressure matter when diagnosing this code?
On engines tested with Service ADVISOR's Harness Diagnostic Mode Test, the code can display during that test only when fuel rail pressure is below 5 MPa (725 psi), which is worth keeping in mind if you're trying to reproduce or verify the fault during testing.