How to Clear SPN 5246 Fault Code and Reset Your Aftertreatment System
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If your truck is stuck in derate and flashing the dreaded SPN 5246 FMI 0 or SPN 5246 FMI 15, it’s usually related to your aftertreatment system—most often the result of a failed regen, DEF quality issue, or a sensor problem.
Here’s how to clear SPN 5246 using a diesel laptop and get your truck back on the road.
🛠 What You’ll Need:
🔄 Step-by-Step: Clear SPN 5246
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Connect your adapter to the truck and launch your diagnostic software
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Establish connection with the ECM
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Check for additional codes (common companion faults: SPN 3364, SPN 3058, SPN 4334)
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If regen was recently interrupted, attempt to run a parked regen
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Once soot level and temp are normal, go to the fault code list
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Select SPN 5246 and click “Clear Code” or “Reset Aftertreatment System”
⚠️ Still Won’t Clear?
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Make sure all sensors (DEF level, NOx, temp) are functioning
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Check that there are no DEF quality or dosing errors
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Ensure no blocked lines or frozen DEF
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A failed component (e.g. NOx sensor or DEF module) may require replacement before the code will clear
💡 Pro Tip:
SPN 5246 is a protective code—not always the root issue. You’ll often need to fix the underlying problem before clearing it.
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