Cummins Fault Code 3712 – How to Clear SCR System Derate (SPN 5246 FMI 0)

Cummins Fault Code 3712 – How to Clear SCR System Derate (SPN 5246 FMI 0)

Cummins Fault Code 3712 means your engine is under a derate condition due to aftertreatment system issues, specifically in the Selective Catalytic Reduction (SCR) system. This code is often paired with SPN 5246 FMI 0, which signals that the system has detected an unresolved emissions-related fault.

What Is Fault Code 3712 on a Cummins Engine?

  • Fault Code: 3712

  • SPN: 5246

  • FMI: 0 – Data Valid but Above Normal Operating Range

  • Description: Aftertreatment SCR Operator Inducement — Final Level

In simple terms, the engine is about to or already has entered a severe power derate due to ignored or unresolved emissions system faults.

Symptoms of Fault Code 3712 (SPN 5246 FMI 0)

  • Engine power severely reduced (5 MPH limp mode)

  • Check Engine Light + MIL (Malfunction Indicator Lamp)

  • DEF warnings or countdown to derate

  • Regen not working properly

  • Truck won’t perform a forced regen

Common Causes of Cummins 3712 Fault

  1. Unresolved DPF/SCR codes (like 3375, 3242, 3563, etc.)

  2. Failed or incomplete DPF regen cycles

  3. Clogged diesel particulate filter (DPF)

  4. Faulty NOx sensors or DEF dosing issues

  5. Excessive soot or high ash content in the aftertreatment system

How to Fix and Clear Cummins Fault Code 3712

  1. Scan for Active and Inactive Codes

    • Use a diesel diagnostic laptop (Insite, Universal Diag, Diesel Tech)

    • Focus on codes like 3375, 1921, 3242, and 3563

  2. Resolve All Underlying Faults

    • Fault Code 3712 is a result—not a root cause

    • Clear the base issues (like failed sensors or high soot levels)

  3. Perform a Forced Regen

    • After fixing root faults, trigger a parked or stationary regen

    • Must be done with a proper RP1210 device and compatible software

  4. Clear the 3712 Code

    • Once the regen completes and all faults are cleared, reset the ECM

    • If the code doesn’t clear, the ECM still sees an unresolved problem

Required Tools

  • RP1210 adapter (Nexiq USB-Link 2, Cummins Inline 6)

  • Cummins Insite or aftermarket software like Universal Diag

  • Laptop scanner kit with forced regen capability

  • Multimeter for wiring tests if sensors are suspected

Pro Tip:

Fault Code 3712 is time-based. If the truck hasn’t completed a successful regen within the required interval, it will trigger this code—even if the filters aren’t fully clogged yet.

Final Thoughts

If your Cummins is stuck with Fault Code 3712 (SPN 5246 FMI 0) and your truck won’t go over 5 MPH, you’re in derate mode due to emissions system faults. You must use a diesel scanner to identify and fix the root problem, then run a regen to fully clear the code.

Don't just clear 3712 — fix the cause first.

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