Code Details
| Display code | SPN 5246 FMI 31 |
|---|---|
| SPN | 5246 |
| FMI | 31 |
| OEM code | None listed |
| Manufacturer | Ford |
| System | Aftertreatment �?SCR system |
| Component | SCR catalyst / NOx sensors |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-11 |
Plain-English Meaning
The Ford 6.7L Power Stroke SCR system measures efficiency using upstream and downstream NOx sensors. When conversion falls below the required threshold, the PCM logs low efficiency and starts the inducement countdown. This code is common at high mileage or after DEF quality issues have affected the catalyst. On Ford F-250 through F-550 Super Duty trucks with the 6.7L Power Stroke, the SCR system is managed by the PCM. Ford IDS and FDRS display DEF quality sensor readings, NOx sensor data, and the SCR efficiency calculation. The 6.7L Power Stroke uses a DEF supply pump that can wear over time, reducing the delivery rate to the dosing injector. A supply pump that delivers below the commanded rate produces sub-threshold SCR efficiency even with good DEF quality. Ford IDS can run a DEF supply pressure test to confirm pump output.
SPN 5246 is Aftertreatment 1 SCR Conversion Efficiency in J1939. FMI 31 indicates the condition exists. On the Ford 6.7L Power Stroke, the PCM monitors the NOx sensor ratio over defined drive cycles. Causes include catalyst degradation from age or heat, poisoning from contamination, DEF quality issues, dosing system faults, and sensor drift. Ford IDS or FDRS provides the diagnostic data needed for a systematic evaluation.
Common Symptoms
- Wrench indicator or check engine lamp active
- SCR system warning on the instrument cluster display
- Inducement counter running in Ford service tools or fleet telematics
- No immediate driveability change at initial fault set
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- SCR catalyst degraded from high mileage or thermal damage
- Catalyst poisoned by oil or coolant contamination
- Chronic DEF quality issues reducing conversion performance
- DEF dosing system fault causing insufficient reagent delivery
- NOx sensor drift on either the upstream or downstream sensor
First Checks
- Connect Ford IDS or FDRS and review all active codes, NOx sensor live data, and DEF quality history
- Compare upstream and downstream NOx readings at operating temperature
- Test DEF dosing module function via Ford diagnostic service routines
- Inspect exhaust system for contamination sources
- Use Ford IDS to run the DEF supply pressure test and confirm the pump output is within specification
- Check the DEF supply line for kinks or freezing damage that would restrict flow to the dosing injector
Can I Keep Driving?
The Ford 6.7 Power Stroke can typically continue operating with this fault active, but the inducement timer is running. Diagnose and resolve before the derate threshold is reached to avoid operational disruption.
Related Codes
Related Lookup Pages
Sources
- Ford Trucks Service Support Public Resources Ford Motor Company · oem · accessed 2026-06-11 · confidence medium
Source: Ford Motor Company, Ford 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
Is the Ford 6.7 Power Stroke SCR catalyst the same as used in the F-250 through F-550?
The 6.7L Power Stroke platform is used across the F-250 through F-550 Super Duty series and some commercial chassis applications. The SCR catalyst design is shared across the platform family, though specific component part numbers and physical dimensions may vary by application weight class.
Can SPN 5246 FMI 31 on the Ford 6.7 be caused by using cheap or off-brand DEF?
Consistently using substandard DEF that is not ISO 22241 compliant can degrade SCR catalyst performance over time. The catalyst needs a steady supply of correctly concentrated DEF to maintain its NOx conversion capability. Using verified ISO 22241 DEF from a reputable supplier is part of preventing premature SCR catalyst degradation.
Does the Ford 6.7 Power Stroke have a specific SCR catalyst cleaning procedure?
SCR catalysts on the Ford 6.7 Power Stroke are not typically cleaned in the field �?they are inspected and replaced if degraded. Unlike the DPF, the SCR catalyst does not accumulate combustible soot. If the catalyst substrate is confirmed as the root cause of low efficiency, the unit requires replacement.