John Deere Engines SPN656FMI7 Fault Code: Injector #6 Not Responding
Also called Cylinder #6 EI Fuel Delivery Failure, Cylinder #6 EI Mechanical Failure
Injector #6 Not Responding · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 656 FMI 7 (also shown as DTC 000656.07) means the ECU does not see a drop in fuel rail pressure when cylinder #6's electronic injector fires. The engine will run rough and misfire on that cylinder. It is a Warning level code, not an immediate shutdown, but it should not be ignored.
Medium severity. This sets as a Warning level alarm. The engine keeps running but will miss on cylinder #6, causing rough running, lost power, and possible long-term wear if left unaddressed. Diagnose within the shift rather than continuing extended operation.
What does John Deere Engines error code SPN656FMI7 mean?
This code is about the high pressure common rail fuel system on John Deere diesel engines (documented on 8.1L, 6.8L, and 4.5L variants). Fuel is delivered to each cylinder by an electronic injector (EI) fed from the high pressure common rail. The ECU controls each injector's Two-Way Valve (TWV), which opens and closes the injector's internal spill valve to control when and how much fuel is injected.
On these engines, injectors share power wiring in groups (cylinders 1,2,3 on one common wire and 4,5,6 on another for the 6-cylinder engines), while the ECU switches each injector's individual ground circuit to fire it. SPN 656 FMI 7 sets specifically for cylinder #6: when the ECU commands that injector to fire, it expects to see a corresponding drop in fuel rail pressure. If that pressure drop does not happen, the ECU concludes the #6 injector isn't actually delivering fuel, even though it was commanded to.
The practical effect is that cylinder #6 misses. The engine will run rough and misfire because that cylinder isn't getting usable fuel delivery, even if the command signal to the injector is correct.
Common causes of SPN656FMI7
- Bad terminals or connector at the ECU
- Bad terminals or connector at the EI (injector) wiring harness
- Restricted fuel line between the high pressure common rail (HPCR) and the inlet to the #6 injector, including leaks, pinches, bends, or cracks in the fuel supply line
- Bad flow limiter
- Bad fuel line fitting at the #6 injector
- Bad fuel inlet connector at the #6 injector
- Loose retaining nuts at the #6 injector
- Bad #6 injector, including dirty injectors
- Bad ECU or bad ECU software
- Incorrect high pressure pump timing
- Failed cylinder cutout test, cylinder misfire test, or injector fuel leak off test result
How to troubleshoot John Deere Engines SPN656FMI7: first checks
- Visually inspect the ECU connectors for contamination, damage, or poor seating
- Inspect the injector harness connector located at the side of the cylinder head for contamination, damage, or poor positioning
- Check all wiring between the ECU and the #6 injector for chafing, corrosion, or damage
- Inspect the fuel line between the high pressure common rail and the #6 injector inlet for leaks, pinches, bends, or cracks
- Check the fuel line fitting and fuel inlet connector at the #6 injector, and confirm the injector retaining nuts are torqued and not loose
- Run cylinder cutout, cylinder misfire, and injector fuel leak off tests if your diagnostic software supports them, to help isolate whether the injector or the fuel supply is at fault
How the code clears
No separate clearing step is listed. This code is active whenever the ignition is on and the fault condition is present, and it should clear on its own once the underlying wiring, fuel line, or injector issue is repaired. Verify repair by clearing codes and confirming the engine runs smoothly without the code resetting during operation.
Frequently asked questions
What does SPN 656 FMI 7 mean on a John Deere engine?
It means the ECU commanded the #6 cylinder's electronic injector to fire, but did not detect the expected drop in fuel rail pressure that should happen when fuel is actually injected. The ECU treats this as a fuel delivery or mechanical failure at that injector.
Can I keep driving or running the equipment with this code active?
The alarm level is listed as a Warning, so the engine will keep running, but it will run rough and misfire on cylinder #6. Continued operation risks poor performance and added wear, so it's best to diagnose and repair as soon as practical.
Is this the same as DTC 000656.07?
Yes. DTC 000656.07 and SPN 656 FMI 7 refer to the same fault, just displayed in different diagnostic formats depending on the tool or engine documentation.
What's the most common cause of this code?
Documented causes point to either wiring and connector problems (at the ECU or injector harness), fuel line restrictions or leaks between the high pressure common rail and the #6 injector, or a failing #6 injector itself. Loose retaining nuts and a bad flow limiter are also listed as possible causes.
Could this be an ECU problem instead of an injector problem?
Yes. A bad ECU or bad ECU software is listed among the possible causes, in addition to injector and fuel line issues. If injector and wiring checks come back clean, ECU software or hardware should be considered.
Will this code cause the engine to shut down?
No shutdown behavior is listed. The documented control unit response is that the engine will run rough and misfire at cylinder #6, not that it will shut down or derate.
What should I inspect first if I get this code?
Start with a visual inspection of the ECU connectors and the injector harness connector at the side of the cylinder head, checking for contamination, damage, or poor positioning, along with the wiring and fuel line running to the #6 injector.