International SPN 1322 FMI 31: Multiple Cylinder Misfire Detected
SPN 1322 FMI 31 (FMI 31) — Engine Misfire for Multiple Cylinders - Condition Exists
Quick Answer
SPN 1322 FMI 31 means the ECM has detected misfire on more than one cylinder on an International A26. It's a High severity fault - the truck is drivable but running rough, and the cause is usually a shared fuel, air, or wiring issue.
Overview: International SPN 1322 FMI 31
ProfessionalDieselRepair.com applies the same discipline to this A26 code as any other platform's multi-cylinder misfire fault - the code is telling you the problem is shared, not isolated to one injector.
Repair Snapshot
Time
2 - 6 Hours
Difficulty
Advanced
Parts Cost
$100 - $2,500
Dealer Labor
$900+
Tools Required
- OEM Diagnostic Software
- Diesel Laptops JPRO
- Multimeter
- Fuel Pressure Gauge
What SPN 1322 FMI 31 Means
SPN 1322 FMI 31 on an International A26 means the misfire monitor has detected activity across more than one cylinder at once. Like on other J1939 platforms, this points toward a shared cause - fuel supply, wiring, or intake - rather than a single bad injector.
Symptoms Drivers Notice
- Rough idle or a noticeable shake felt through the cab
- Check engine light, often with individual cylinder misfire codes alongside it
- Loss of power and poor fuel economy
- Excessive white or black smoke depending on which cylinders are affected
Most Likely Root Causes
Restricted or contaminated fuel supply
CommonA mechanical fuel delivery issue - low or fluctuating supply pressure can starve several injectors at once, especially under load.
Chafed or corroded shared harness ground or power feed
CommonAn electrical fault where a single damaged wire on a shared circuit causes intermittent misfire signatures across multiple cylinders.
Marginal crankshaft or camshaft position sensor signal
OccasionalA sensor/signal-quality issue rather than a true combustion problem - a noisy timing signal can cause false misfire logging across cylinders.
Air intake restriction or boost leak
OccasionalA mechanical airflow issue that can cause lean misfire conditions spread across multiple cylinders.
Common Misdiagnoses (Don't Waste Parts)
Replacing individual injectors one at a time based on misfire counts
Why it happens: It feels like a direct, isolated fix.
Do this instead: That's a parts-cannon approach for a multi-cylinder code - verify shared fuel supply, harness integrity, and timing signal quality first.
Assuming a boost leak can't cause misfire on a diesel
Why it happens: Misfire feels like a purely fuel-related problem to many techs.
Do this instead: Run a boost leak test - a significant intake leak can cause lean misfire conditions that mimic fuel or injector problems.
Master Tech Commentary
Mechanic's Notes
ProfessionalDieselRepair.com note: when misfire shows up on multiple cylinders at once, resist the urge to start swapping injectors. Work the shared systems - fuel supply, harness grounds, cam/crank signal quality - before you ever isolate down to a single injector.
Step-by-Step Diagnostic Procedure
- Step 1: Pull the full fault list with a scan tool - look for which specific cylinder SPNs are logging alongside this multi-cylinder code.
- Step 2: Check fuel supply pressure and filter condition first, since a restricted supply commonly affects multiple cylinders at once rather than just one.
- Step 3: Inspect the injector harness and connectors for a shared ground or power wire that could affect several cylinders if chafed or corroded.
- Step 4: Run individual injector cutout tests to see if misfires cluster on one bank or side, which often points to a harness or fuel rail issue on that side.
- Step 5: If cylinders are scattered with no pattern, check crankshaft and camshaft position sensor signal quality, since a marginal timing signal can register as false misfire across multiple cylinders.
Professional service / OEM-level scan tools are recommended before clearing this fault for good.
Live Data & Freeze-Frame Tips
Log individual cylinder misfire counts side by side with fuel rail pressure and boost pressure during a road test. Misfires that spike when rail pressure dips under load point to a supply issue rather than an injector-specific fault.
Safety Warnings
- Relieve fuel system pressure before disconnecting injector lines or rail fittings.
- Allow the engine to cool before working near the exhaust manifold and turbo.
When to Limp In vs Tow
Not usually necessary - the truck remains drivable, though expect rough running and reduced fuel economy until the shared cause is identified and repaired.
Prevention Tips for Fleets & Owner-Operators
- Keep fuel filters and water separators on schedule to protect supply pressure to all cylinders.
- Inspect injector harnesses for chafing at routine PM intervals.
- Address boost leaks and intake restrictions promptly rather than letting them linger.
Related Fault Codes
SPN 5357 FMI 0
Fuel injection quantity error across multiple cylinders, a related fueling issue that can accompany or cause misfire.
SPN 8064 FMI 12
A crankshaft position signal fault that can cause false misfire logging if the timing signal is marginal rather than fully lost.
Frequently Asked Questions
Can I keep driving with this code active?
Yes, but expect a rough idle and reduced power. Continued driving with unresolved misfire can lead to unburned fuel affecting the aftertreatment system over time.
How do I reset this code without a scan tool?
A battery disconnect may clear it temporarily, but it returns on the next misfire event if the shared cause isn't fixed.
What triggers a derate from this code?
Severe or sustained multi-cylinder misfire can trigger a protective power reduction to prevent unburned fuel from damaging the aftertreatment system.
Is this always a fuel problem?
No - shared wiring faults, a weak timing sensor signal, or a boost leak can all produce the same multi-cylinder pattern.
How much does this typically cost to fix?
A harness repair or fuel filter service runs $100-$400. If it comes down to multiple injectors, costs can climb toward $2,000-$2,500.
Should I replace all the injectors at once?
Not without confirming which cylinders are truly at fault mechanically - replacing injectors that were never bad wastes money on what's often a shared-system problem.