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SPN 3936 FMI 16

Aftertreatment 1 DPF System — Value too high (moderately severe).
The reading is above normal at a middle warning level — more serious than FMI 15, less than FMI 0.

What the SPN covers: A summary fault for the diesel particulate filter system, usually set when regenerations are not keeping soot under control. More on SPN 3936.

What FMI 16 usually points to: A developing over-condition that often precedes a derate. More on FMI 16.

Severity

HIGH — limit use, diagnose now

Often comes with escalating derates. Fix the cause and regenerate before the DPF overloads.

Likely causes

  1. Regeneration requested but not completed
  2. Exhaust temperature sensor or DOC problem stopping regen
  3. Cracked or plugged DP sensor hoses
  4. Engine making excess soot
  5. Ash-loaded DPF needing cleaning

Checks & fixes (easiest first)

  1. Review regen history (frequency, completed vs. aborted)
  2. Check the exhaust temperature sensors and DOC light-off during a parked regen
  3. Inspect DP sensor tubes and hoses inside and out
  4. Have the DPF cleaned or weighed if ash-loaded

FAQ

What does SPN 3936 FMI 16 mean?

Aftertreatment 1 DPF System — value too high (moderately severe). The reading is above normal at a middle warning level — more serious than FMI 15, less than FMI 0.

Is SPN 3936 FMI 16 serious?

Often comes with escalating derates. Fix the cause and regenerate before the DPF overloads.

What should I check first for SPN 3936 FMI 16?

Review regen history (frequency, completed vs. aborted); Check the exhaust temperature sensors and DOC light-off during a parked regen; Inspect DP sensor tubes and hoses inside and out.