Code Details
| Display code | SPN 5246 FMI 31 |
|---|---|
| SPN | 5246 |
| FMI | 31 |
| OEM code | None listed |
| Manufacturer | Volvo |
| System | Aftertreatment �?SCR system |
| Component | SCR catalyst / DEF dosing system |
| Source address | Unknown or not applicable |
| Severity | medium |
| Review status | source backed |
| Source confidence | medium |
| Last reviewed | 2026-06-11 |
Plain-English Meaning
The SCR system converts NOx from the exhaust into harmless nitrogen and water using DEF. The efficiency is measured by comparing NOx levels before and after the SCR catalyst. When the conversion rate falls below the required threshold, this fault sets and an inducement sequence may begin. On Volvo VNL 860 and VHD trucks with the D16, the larger displacement engine produces proportionally more NOx than the D13, placing higher demand on the SCR catalyst and DEF dosing system. VCADS Pro displays upstream and downstream NOx sensor values alongside the calculated SCR efficiency metric. The D16 dosing injector tip is exposed to high exhaust temperatures and is susceptible to coking from DEF mineral deposit buildup. Inspecting the dosing injector tip and cleaning or replacing it is a common first action when SPN 5246 FMI 31 appears on a D16 with otherwise good DEF quality.
SPN 5246 FMI 31 is the SCR Operator Inducement Severity parameter indicating an active SCR compliance issue. On the Volvo D16 with EMS3 and ACM2.0 control, VCADS Pro provides upstream and downstream NOx sensor data, DEF dosing quantity, SCR inlet temperature, and DEF quality to enable a complete efficiency diagnosis. Low temperature operation that inhibits DEF dosing can cause temporary efficiency drops in demanding duty cycles.
Common Symptoms
- SCR or aftertreatment warning lamp active
- Inducement countdown visible in VCADS Pro
- Possible progressive derate if inducement condition is not resolved
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- DEF quality below the minimum acceptable concentration
- Plugged DEF dosing injector preventing adequate DEF delivery
- Degraded or thermally aged SCR catalyst with reduced conversion capacity
- NOx sensor fault causing incorrect efficiency calculation
- DEF supply pump fault limiting DEF delivery
First Checks
- Connect VCADS Pro and monitor DEF dosing quantity, SCR inlet temperature, and upstream/downstream NOx simultaneously
- Verify DEF quality using VCADS Pro sensor data and confirm ISO 22241 compliant DEF is in the tank
- Check DEF dosing injector with a VCADS Pro purge command
- Inspect the DEF supply circuit for blockages or leaks
- Inspect the DEF dosing injector tip for coking or mineral deposit buildup
- Compare upstream and downstream NOx values in VCADS Pro to assess catalyst efficiency independently
Can I Keep Driving?
The inducement sequence may be active or accumulating. The D16 is still driveable at this stage, but the derate will worsen if the underlying SCR fault is not resolved.
Related Codes
Related Lookup Pages
Sources
- Volvo Trucks Tech Info Public Resources Volvo Trucks North America · oem · accessed 2026-06-11 · confidence medium
Source: Volvo Trucks North America, Volvo Trucks Tech Info Public Resources. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - Volvo Trucks / Mack Trucks Technical Support Volvo Trucks North America / Mack Trucks Inc. · oem · accessed 2026-06-10 · confidence medium
Source: Volvo Trucks North America / Mack Trucks Inc., Volvo Trucks / Mack Trucks Technical Support. 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 SCR dosing injector the same part on the Volvo D16 and D13?
The D16 and D13 use similar Volvo aftertreatment architecture with comparable dosing injector designs. Part numbers may differ to account for different aftertreatment system sizing. VCADS Pro part look-up or the Volvo parts portal can confirm the correct injector part number for the specific model year and engine.
Can high altitude operation affect SCR efficiency on the Volvo D16?
High altitude reduces ambient air density, which can affect combustion characteristics and engine-out NOx levels. While the aftertreatment system is designed to operate across a wide range of conditions, extreme altitude combined with heavy load and cold ambient temperatures can challenge the SCR system's ability to maintain temperature-dependent efficiency targets.
How does the Volvo D16's SCR efficiency monitoring compare to the D13?
The monitoring methodology is the same �?upstream and downstream NOx sensors with an efficiency ratio calculation. The D16's larger displacement and higher potential NOx output means the absolute quantity of DEF needed is higher, but the percentage-based efficiency threshold and the diagnostic approach via VCADS Pro are essentially identical to the D13.