Code Details
| Display code | SPN 3246 FMI 0 |
|---|---|
| SPN | 3246 |
| FMI | 0 |
| OEM code | None listed |
| Manufacturer | Cummins |
| System | Aftertreatment �?DPF |
| Component | DPF / DPF outlet temperature sensor / regeneration system |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-12 |
Plain-English Meaning
During active DPF regeneration, temperatures inside the DPF can reach 550�?50°C to burn off accumulated soot. When outlet temperature exceeds the normal ceiling �?often above 700°C �?the ECM logs SPN 3246 FMI 0. This can happen when the DPF is severely loaded and requires a more intense regen cycle, when an overly rich combustion condition is feeding excess unburned fuel to the aftertreatment system, or when the DPF outlet temperature sensor is giving an incorrect high reading.
SPN 3246 FMI 0 is Aftertreatment 1 DPF Outlet Temperature above normal operating range. On Cummins CM2350, the ECM monitors the DPF outlet temperature as a safety control parameter. If temperature exceeds the protection threshold, the ECM may abort the active regen cycle or reduce fuel delivery to the dosing injector. Insite can display the complete temperature profile during regen �?inlet, mid-bed, and outlet �?to identify where the heat load is concentrated.
Common Symptoms
- Check engine or DPF warning during or after a regeneration cycle
- Regeneration aborted mid-cycle in some cases
- High exhaust temperature lamp if equipped
- DPF soot load may be elevated prior to the high-temp event
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- DPF heavily loaded with soot requiring a prolonged high-intensity regen cycle
- Overly rich combustion condition sending excess hydrocarbons to the aftertreatment system
- DPF dosing injector fault causing over-injection of fuel during active regen
- DPF outlet temperature sensor reading high due to fault or heat soak
- DPF partially plugged with ash requiring service cleaning
First Checks
- Connect Cummins Insite and check the DPF soot load percentage and regen history
- Review the DPF inlet and outlet temperature profiles during the event using Insite fault snapshots
- Inspect the DPF outlet temperature sensor for proper reading �?compare to inlet sensor during normal operation
- Check for rich combustion companion codes (e.g., SPN 157, SPN 94) that could indicate fuel delivery issues affecting regen quality
- Confirm the last DPF cleaning record �?ash-loaded DPFs generate higher temperatures during regen
Can I Keep Driving?
Engine may remain driveable but regen cycles may be interrupted. Continued operation with high DPF outlet temperatures can shorten DPF and SCR catalyst life.
Related Codes
Related Lookup Pages
Sources
- Cummins INSITE Service Tool — Public Reference Documentation Cummins Inc. · oem · accessed 2026-06-11 · confidence medium
Source: Cummins Inc., Cummins INSITE Service Tool — Public Reference Documentation. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - QuickServe Online Cummins Inc. · oem · accessed 2026-05-05 · confidence medium
Source: Cummins Inc., QuickServe Online. 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 hot should the Cummins ISX15 DPF outlet get during a normal active regen?
During a normal active regeneration, DPF outlet temperatures on the ISX15 and X15 can reach 550�?50°C. SPN 3246 FMI 0 is triggered when the outlet temperature exceeds the calibrated upper limit, which is typically above 700°C. Temperatures in the normal regen range are expected and do not cause this fault.
Can missing a requested regen cause DPF outlet temperature to go high?
Yes. When a regen request is repeatedly inhibited or ignored, the DPF soot load continues to build. When a regen eventually occurs with a heavily loaded DPF, the burn-off generates more heat, potentially exceeding the outlet temperature limit. Following the regen indicator and not inhibiting regens when safe to allow them helps prevent over-temperature events.
Does SPN 3246 FMI 0 always require DPF replacement on the Cummins ISX15?
Not always. If the high temperature was a one-time event from an unusually soot-loaded DPF that completed a full regen, the DPF may continue to function normally. However, repeated high-temperature events can damage the DPF substrate and SCR catalyst. Insite's regen history and DPF pressure differential data help assess whether the filter is degraded.