General Association
SPN 4094 may be displayed in a NOx or SCR monitoring context. SPN labels and diagnostic trees can vary by OEM, module, calibration, and model year.
Common FMI Combinations
Record the FMI with the SPN. FMI values help distinguish high or low voltage, abnormal update rate, data erratic, threshold conditions, or manufacturer-specific logic.
Systems Often Involved
This topic is commonly discussed with aftertreatment diagnostics, related sensors, wiring, power supply, grounds, module communication, and software strategy.
What To Record
Record SPN, FMI, source address, active or inactive status, warning lamps, derate state, related codes, operating conditions, mileage, and engine hours.
Why OEM Confirmation Matters
A standalone SPN number is not enough for a repair decision. Use official service information and diagnostic software for the final interpretation.
Related Pages
Sources
- 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 - Cleaner Trucks Initiative and Heavy-Duty Engine Emissions Context United States Environmental Protection Agency · government · accessed 2026-05-05 · confidence medium
Source: United States Environmental Protection Agency, Cleaner Trucks Initiative and Heavy-Duty Engine Emissions Context. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
Is SPN 4094 a repair instruction page?
No. It is an educational reference that helps drivers and fleets record useful diagnostic information before using OEM service information or a qualified technician.
Can SPN 4094 identify one failed part?
Usually no. Fault codes, symptoms, and system names point to monitored conditions. The root cause should be verified with the full code set, active status, related codes, and official diagnostic information.
What should I record when using this spn page?
Record the exact message or code, active or inactive status, warning lamps, derate condition, mileage, engine hours, and any recent service or operating conditions.