International SPN 655 FMI 5: Injector Cylinder #5 Open Circuit
SPN 655 FMI 5 (FMI 5) — Engine Injector Cylinder #5 - Current Below Normal or Open Circuit
Quick Answer
SPN 655 FMI 5 means the International ECM sees an open circuit in the cylinder #5 injector driver and cannot fire that injector. It's a High severity fault causing a rough idle and power loss, but it does not shut the engine down.
Overview: International SPN 655 FMI 5
International's A26 and N13 engines follow the same J1939 injector cylinder numbering convention as other heavy-duty platforms, with SPN 655 flagging cylinder #5 specifically. FMI 5 points to current below normal, the classic electrical signature of an open circuit rather than a short. ProfessionalDieselRepair.com covers this fault frequently since valve cover harness chafing is such a consistent root cause across nearly every OEM platform that uses individual cylinder injector fault codes.
Repair Snapshot
Time
1.5 - 3 Hours
Difficulty
Intermediate
Parts Cost
$50 - $620
Dealer Labor
$500+
Tools Required
- Diesel Laptops Diagnostic Software
- Multimeter
- Jaltest Diagnostic Tool
- Valve Cover Gasket Set
What SPN 655 FMI 5 Means
SPN 655 FMI 5 means the International engine ECM has detected an open circuit in the cylinder #5 injector driver and cannot fire that injector. The truck keeps running on the remaining cylinders with a rough idle and reduced power, and the amber MIL illuminates immediately. This is not a shutdown fault, but continued operation with a disabled cylinder risks fuel dilution of the engine oil over time.
Symptoms Drivers Notice
- Rough idle with a miss traceable to cylinder #5
- Amber MIL illuminated
- Reduced power and fuel economy
- Possible white smoke from unburned fuel at the affected cylinder
Most Likely Root Causes
Chafed valve cover harness wire
CommonVibration wears through insulation where the harness routes near rocker arm hardware, eventually breaking the conductor completely.
Corroded or loose injector connector
CommonMoisture intrusion or an improperly seated locking tab creates a high-resistance or open contact the ECM reads as a dead circuit.
Failed injector solenoid winding
OccasionalInternal solenoid coil failure from heat and vibration fatigue can open the circuit after extended service life.
ECM injector driver stage failure
RareAn internal ECM fault on that specific driver channel would show the same code, but only after the injector and harness both test clean.
Common Misdiagnoses (Don't Waste Parts)
Ordering a replacement injector before checking harness continuity
Why it happens: A parts-cannon shortcut assumes the injector is automatically the failure point since it's named in the fault description.
Do this instead: Ohm out the injector at the connector and check harness continuity back to the ECM before committing to an injector replacement.
Assuming rough idle always means a fuel filter or fuel quality issue
Why it happens: Rough idle symptoms get blamed on fuel delivery generally without pulling codes first.
Do this instead: Scan for active codes before chasing fuel delivery components, since a single dead cylinder produces very similar symptoms.
Not checking the locking tab engagement on the injector connector
Why it happens: A quick visual check can miss a connector that appears plugged in but isn't fully locked.
Do this instead: Physically confirm the connector cannot be pulled apart by hand before proceeding to more invasive diagnostics.
Master Tech Commentary
Mechanic's Notes
Shop tip from ProfessionalDieselRepair.com: on International engines with A26 or N13 power, valve cover harness chafing is the single most common cause of a single-cylinder injector fault. Always ohm out the injector at the connector before pulling the valve cover for a harness inspection - it takes five minutes and can save an unnecessary teardown.
Step-by-Step Diagnostic Procedure
- Step 1: Connect a compatible International diagnostic tool and confirm SPN 655 FMI 5, then run a cylinder cutout test to verify cylinder #5 contributes nothing.
- Step 2: Shut down and unplug the cylinder #5 injector connector, checking for corrosion, bent pins, or a loose locking tab.
- Step 3: Measure resistance across the injector solenoid terminals with a multimeter and compare to the engine manufacturer's spec.
- Step 4: If the injector reads good, trace the harness back toward the ECM for chafing near the valve cover or rocker assembly.
- Step 5: Repair or replace the faulty component, clear the code, and re-run the cutout test to confirm cylinder #5 is firing correctly before road testing.
Live Data & Freeze-Frame Tips
Run the cylinder cutout test on your diagnostic tool and confirm cylinder #5 shows zero RPM contribution. Watching injector driver status while wiggling the harness near known chafe points can help catch an intermittent open circuit before it becomes permanent.
Safety Warnings
- Never probe injector connectors with the engine running due to high transient voltages during firing.
- Allow the engine to cool before working near the valve cover.
- Disconnect batteries before disturbing injector wiring.
- Wear safety glasses when cleaning connector pins with contact cleaner.
When to Limp In vs Tow
Towing is generally not needed since the truck will still drive with reduced power. Consider towing if additional misfire or fuel pressure codes appear alongside it, suggesting a broader fuel system problem.
Prevention Tips for Fleets & Owner-Operators
- Inspect valve cover harnesses for chafing at every major PM interval.
- Re-secure harness clips any time the valve cover is removed for service.
- Use dielectric grease on injector connectors during reassembly.
- Address rough idle complaints early before they progress to a hard fault code.
Related Fault Codes
SPN 654 FMI 5
Same fault type but for the adjacent cylinder #4 injector circuit.
SPN 655 FMI 6
Current above normal (shorted) on the same cylinder #5 injector circuit rather than open.
SPN 8064 FMI 12
A known International-specific fault code worth checking for correlation on engines with recurring injector issues.
Frequently Asked Questions
Can I drive with SPN 655 FMI 5 active?
Yes, the truck will drive with a rough idle and reduced power since the ECM has disabled that cylinder's injector. It's not a shutdown code, but repair is recommended soon.
How do I reset SPN 655 FMI 5 without a scanner?
A battery disconnect may clear it temporarily, but the fault returns on the next drive cycle if the open circuit hasn't actually been repaired.
Does this code trigger a derate?
Some calibrations apply a mild power reduction with a disabled cylinder, but it's not the aggressive emissions inducement derate seen with aftertreatment faults.
What's the difference between FMI 5 and FMI 6 here?
FMI 5 means current below normal, typically an open circuit or broken wire. FMI 6 means current above normal, typically a short to power or ground. Both affect the same circuit but represent opposite electrical failure modes.
Can a bad ground cause this code?
Yes, since injector solenoids are grounded through the ECM driver circuit, a corroded or broken ground path reads identically to an open supply wire on a resistance test.
Is it safe to drive a few days with a dead cylinder?
Short-term driving is generally fine, but extended operation with a disabled cylinder risks fuel washing down the cylinder wall and diluting engine oil, so timely repair is worthwhile.