International SPN 651 FMI 5: Cylinder #1 Injector Circuit Open
SPN 651 FMI 5 (FMI 5) — Engine Injector Cylinder #1 - Current Below Normal or Open Circuit
Quick Answer
SPN 651 FMI 5 means the cylinder #1 injector solenoid circuit is open, causing a misfire on that cylinder. This is a high-severity code with noticeable power loss and rough running - check the valve cover harness before replacing the injector.
Overview: International SPN 651 FMI 5
A single dead cylinder shows up fast in the way a truck runs, and this code points the finger right at it. ProfessionalDieselRepair.com always checks the valve cover harness pass-through first, since that's a well-known chafe point on MaxxForce engines that produces the exact same fault as a failed injector.
Repair Snapshot
Time
2 - 4 Hours
Difficulty
Advanced
Parts Cost
$300 - $900
Dealer Labor
$700+
Tools Required
- Jaltest Diagnostic Tool
- Diesel Laptops Scan Tool
- Multimeter
What SPN 651 FMI 5 Means
SPN 651 FMI 5 means the ECM commanded cylinder #1's injector solenoid but detected insufficient current flow, consistent with an open circuit. On International MaxxForce/A26 engines this typically causes a noticeable misfire on that cylinder along with rough running and reduced power.
Symptoms Drivers Notice
- Amber or red warning lamp with active misfire on cylinder #1
- Rough idle and noticeable engine shake at low RPM
- Noticeable power loss and possible white smoke from unburned fuel
- Increased fuel consumption from the cylinder not firing correctly
Most Likely Root Causes
Chafed or broken wire at the valve cover harness grommet
CommonThe harness pass-through point at the valve cover is a known wear spot where insulation rubs through over time, breaking the injector circuit.
Failed injector solenoid
OccasionalInternal solenoid winding failure directly opens the circuit and requires injector replacement.
Corroded or damaged injector connector
OccasionalMoisture intrusion at the connector can corrode pins enough to open the circuit intermittently or permanently.
Common Misdiagnoses (Don't Waste Parts)
Replacing the injector without checking the valve cover harness
Why it happens: A parts-cannon assumption that any injector circuit code means the injector itself failed, skipping the well-documented harness chafe point.
Do this instead: Inspect and test the valve cover harness continuity first - a broken wire at the grommet produces the identical fault and is a far cheaper fix.
Master Tech Commentary
Mechanic's Notes
Shop tip: ProfessionalDieselRepair.com always checks the valve cover harness for chafing at the grommet before condemning the injector on this code - a worn harness pass-through is a well-documented weak point on MaxxForce platforms and mimics an open injector solenoid perfectly.
Step-by-Step Diagnostic Procedure
- Step 1: Pull the fault and freeze-frame data on Navistar's diagnostic software or a comparable Jaltest connection to confirm cylinder #1 is the affected injector.
- Step 2: Inspect the injector #1 connector for corrosion, looseness, or heat damage at the valve cover harness.
- Step 3: Back-probe the injector solenoid circuit with a multimeter, key on engine off, to check for continuity through the driver circuit.
- Step 4: Measure injector solenoid resistance at the connector and compare against OEM specification, typically in the low single-digit ohm range.
- Step 5: Trace the wiring from the injector connector back to the ECM valve cover harness for chafing or a broken conductor.
- Step 6: Replace the injector only after confirming the solenoid itself is open, since a harness break produces the identical fault code.
Professional service / OEM-level scan tools are recommended before clearing this fault for good.
Live Data & Freeze-Frame Tips
Use injector cutout testing on Jaltest to confirm cylinder #1 contributes zero RPM drop when commanded, verifying the misfire location matches the fault code before beginning teardown.
Safety Warnings
- Relieve fuel system pressure before disconnecting any injector or fuel line connections.
- Allow the engine to cool before accessing the valve cover harness.
When to Limp In vs Tow
Towing is not typically necessary, but the engine will run rough and underpowered until repaired - avoid heavy load hauling until the misfire is resolved.
Prevention Tips for Fleets & Owner-Operators
- Inspect valve cover harness grommets for wear during scheduled valve adjustment services.
- Keep injector connectors clean and protected from moisture intrusion.
- Address any minor injector circuit warnings promptly before they progress to a full open circuit.
Related Fault Codes
SPN 651 FMI 6
Cylinder #1 injector current above normal/shorted - the opposite electrical fault on the same injector circuit.
SPN 652 FMI 5
Cylinder #2 injector open circuit - the same fault pattern on the adjacent cylinder's injector.
Frequently Asked Questions
Can I keep driving with this code active?
Short distances are possible, but expect a rough-running, underpowered engine. Get it repaired soon since running on a dead cylinder increases wear on other components.
How do I reset this code without a scan tool?
You need Jaltest, Diesel Laptops, or a comparable tool to clear the code after confirming and repairing the injector circuit.
What triggers a derate on this code?
This code doesn't typically trigger a formal ECM derate, but the misfire itself causes a real, noticeable loss of power and roughness.
Is it always the injector that needs replacing?
No, a broken wire at the valve cover harness grommet is a common and cheaper cause than an actually failed injector solenoid.
Will this cause white smoke?
Yes, unburned fuel from the non-firing cylinder can produce white smoke, especially noticeable at startup or idle.
How can I confirm which cylinder is affected?
Use an injector cutout test on your diagnostic tool - cutting out a healthy cylinder causes an RPM drop, while cutting out the already-dead cylinder shows no change.