Code Details
| Display code | SPN 3251 FMI 0 |
|---|---|
| SPN | 3251 |
| FMI | 0 |
| OEM code | None listed |
| Manufacturer | International |
| System | Aftertreatment �?DPF system |
| Component | Diesel particulate filter / differential pressure sensor |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-11 |
Plain-English Meaning
The International A26 DPF captures soot from the exhaust and requires periodic regeneration cycles to stay clean. When soot accumulates faster than regeneration can clear it �?due to short trips, inhibited regens, or EGR issues �?this code sets and a warning lamp appears on the International dash. On International LT Series trucks with the A26, the DPF restriction fault SPN 3251 FMI 0 follows the same escalation path as other Detroit and Cummins engines. The A26 uses Diamond Logic with ServiceMaxx for DPF system management. ServiceMaxx initiates a forced parked regen if the driver-initiated regen does not complete. For fleet LT Series trucks in stop-and-go distribution service, the DPF cleaning service interval should be evaluated periodically based on the actual regen frequency data in ServiceMaxx.
SPN 3251 is Aftertreatment 1 Particulate Trap Differential Pressure in J1939. FMI 0 indicates the estimated soot load exceeds the normal range. On the International A26, the ECM uses differential pressure data and a soot model to estimate DPF loading. International Diamond Logic provides access to soot load, ash load, and regeneration history. A forced regeneration can be initiated through Diamond Logic when conditions are met.
Common Symptoms
- DPF or regen warning lamp on the International instrument cluster
- Frequent or incomplete active regeneration cycles
- Slight reduction in fuel economy under heavy load
- Elevated exhaust backpressure in diagnostic data
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Short-trip or high-idle duty cycle preventing passive regeneration temperatures
- Driver inhibiting or canceling active regeneration cycles
- EGR fault causing increased soot production
- Plugged differential pressure sensor or sensing lines
- High-ash engine oil accelerating DPF loading
First Checks
- Connect International Diamond Logic and review DPF soot load, ash load, and regeneration history
- Perform a stationary forced regeneration using Diamond Logic if soot load is below the critical threshold
- Check differential pressure sensor and lines for blockage
- Confirm engine oil meets Navistar-specified low-ash requirements
- Connect ServiceMaxx and review DPF differential pressure and soot load data
- If parked regen completes but SPN 3251 returns quickly, evaluate DPF for cleaning service
Can I Keep Driving?
At the initial warning stage the A26 can continue operating. Reaching the critical threshold triggers a torque derate. Running to a severe derate risks DPF damage requiring filter replacement.
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 - Navistar Engine Diagnostic Trouble Code Body Builder References Navistar / International Truck Body Builder · oem · accessed 2026-05-05 · confidence medium
Source: Navistar / International Truck Body Builder, Navistar Engine Diagnostic Trouble Code Body Builder References. 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
How does the International A26 DPF system compare to earlier MaxxForce engines?
The A26 uses a more conventional DPF and SCR aftertreatment layout compared to the high-EGR MaxxForce engines, and the aftertreatment system has been more reliable in service. DPF regeneration procedures on the A26 follow standard industry practice and can be performed using International Diamond Logic.
How long does a forced regen take on the International A26?
A stationary forced regeneration on the A26 typically takes 20 to 45 minutes depending on the soot load level. The process requires the engine to be at operating temperature and the vehicle to be parked safely with the exhaust pointed away from flammable materials. Diamond Logic displays progress and any fault conditions during the process.
Can a bad DPF differential pressure sensor cause SPN 3251 FMI 0 on the A26?
Yes. Blocked or damaged differential pressure sensor lines can cause the ECM to calculate an inflated soot load. If a forced regen completes quickly and the fault returns almost immediately, inspect the sensor and its reference tubes for blockage or damage before replacing the DPF.