What is SPN 5246 FMI 15 & How to Solve It?

What is SPN 5246 FMI 15:

SPN 5246 is a reductant system inducement code, often tied to DEF or aftertreatment failure. FMI 15 means a valid signal is above expected range, usually referring to DEF tank level, pressure, or temp.

This code is typically triggered when DEF system conditions are abnormal and the system is preparing to initiate engine derate to prevent emissions violations.

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Why This Happens

• DEF level sensor or quality sensor giving high false reading.
• Software interpreting out-of-range signals.
• Reductant pump running excessively.
• Control unit getting inconsistent DEF data.

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How to Fix It

1. Check DEF fluid level and verify sensor readings.
2. Inspect quality, temp, and pressure sensors in the DEF system.
3. Run diagnostics to confirm data consistency across modules.
4. Replace sensors that are out of spec.
5. Clear the code and confirm system resets out of inducement mode.

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How to Avoid It Before It Happens

1. Maintain DEF sensors and replace them before failure.
2. Refill DEF only from sealed, clean containers.
3. Monitor pressure and temperature data during operation.
4. Log all DEF-related faults for trend analysis.