Code Details
| Display code | SPN 3480 FMI 5 |
|---|---|
| SPN | 3480 |
| FMI | 5 |
| OEM code | None listed |
| Manufacturer | International |
| System | Aftertreatment — DEF dosing system |
| Component | DEF dosing injector / wiring circuit |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-12 |
Plain-English Meaning
The International A26 DEF dosing injector sprays DEF into the exhaust stream to supply the SCR catalyst. FMI 5 means the circuit is open — no current flows through the injector even when the control module commands it to activate. Without DEF dosing, the SCR system stops reducing NOx and the inducement sequence will begin. In most cases this fault traces to a wiring problem or a failed injector solenoid coil.
SPN 3480 is related to Aftertreatment DEF Dosing Unit control in J1939. FMI 5 indicates current below normal or an open circuit in the injector control path. On International A26 engines, the aftertreatment control module drives the DEF dosing injector solenoid. When the module commands the injector and receives no current feedback, SPN 3480 FMI 5 is set. International ServiceMaxx provides an injector actuation test and live circuit monitoring to help distinguish wiring faults from injector coil failures.
Common Symptoms
- SCR efficiency or NOx conversion fault alongside SPN 3480 FMI 5
- DEF dosing activity showing zero or below commanded in ServiceMaxx
- DEF system warning on the International instrument cluster
- Inducement sequence may start if the injector remains inoperative
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Broken or damaged wire in the DEF injector harness
- Corroded or disconnected injector electrical connector
- Failed DEF dosing injector solenoid coil (open circuit)
- Aftertreatment control module output circuit fault
First Checks
- Connect International ServiceMaxx and run the injector actuation test while monitoring circuit response
- Inspect the DEF dosing injector harness and connector for visible damage, corrosion, or moisture
- Measure coil resistance at the injector connector — an open reading confirms a failed internal solenoid
- If coil resistance is within specification, trace the harness from the injector to the control module connector for open circuits or damaged splices
- Replace the DEF dosing injector if coil measurement confirms an internal open
Can I Keep Driving?
The A26 remains driveable with SPN 3480 FMI 5 active, but without DEF dosing the SCR system will not function and the inducement sequence will begin. Repair the circuit fault before inducement escalates to a torque or speed restriction.
Related Codes
Related Lookup Pages
Sources
- International Trucks Service Support Public Resources International Trucks / Navistar International · oem · accessed 2026-06-11 · confidence medium
Source: International Trucks / Navistar International, International Trucks Service Support Public Resources. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium
Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
Where is the DEF dosing injector located on the International A26 in LT Series trucks?
On International LT Series trucks with the A26 engine, the aftertreatment system is typically mounted under the cab or along the frame rail. The DEF dosing injector is threaded into a bung in the exhaust pipe upstream of the SCR catalyst. Exact location varies by chassis configuration. Allow adequate cool-down time before working near the exhaust and injector components.
Can ServiceMaxx perform an injector flow test on the International A26?
ServiceMaxx includes injector actuation and dosing system tests that command the injector to activate while monitoring circuit response and DEF dosing quantity. This allows a technician to confirm whether the injector is electrically open (SPN 3480 FMI 5) or physically blocked (a different fault category). The actuation test is the primary tool for distinguishing circuit faults from mechanical injector problems.
Does SPN 3480 FMI 5 on the A26 require replacing the entire aftertreatment module?
No. SPN 3480 FMI 5 is a circuit fault specific to the DEF dosing injector circuit. In most cases, the repair involves replacing the dosing injector itself or repairing the wiring harness between the injector and the control module. Replacing the entire aftertreatment module would be an extreme measure and is not typically needed for this fault code.