Diesel Trouble Codes

SPN 3719 FMI 16 — Aftertreatment DPF Soot Load – Above Normal, Moderately Severe — Detroit DD15

SPN 3719 FMI 16 is a Detroit DD15 aftertreatment fault for DPF soot load above normal, moderately severe. The ACM/MCM calculates soot load from DPF…

Updated October 15, 2026

What it means

On Detroit DD15 (2010–present) with DOC+DPF+SCR (BlueTec), SPN 3719 FMI 16 means the calculated DPF soot load is above normal, moderately severe. The generic definition is that the calculated DPF soot load is above normal.1

Most likely causes

  1. Interrupted or failed regenerations due to short-trip duty cycles or frequent key-off before regen completion — Short runs prevent the ACM from reaching and sustaining regeneration temperature, so soot accumulates. Review recent drive cycles and ACM regen history for aborted or incomplete parked/on-road regens.1
  2. Engine-side soot production elevated by EGR, injector or air-system faults — Excess soot from combustion or EGR flow issues raises DPF loading faster than normal. Check for accompanying engine faults, EGR flow target errors, boost leaks, and injector-related misfire/roughness indicators via MCM data.1
  3. DPF differential pressure sensor or sensing lines reading falsely high, inflating calculated soot load — Plugged, cracked or moisture-contaminated pressure tubes or a drifting sensor can bias the soot-load model upward. Inspect DPF differential pressure sensor lines and compare live SPN 3251 behavior to expected values.23
  4. Ash accumulation contributing to overall restriction and soot-load model drift — Ash does not burn off in regeneration; high ash raises baseline restriction and can make soot load appear elevated. If ash service interval is due, the DPF may need removal and cleaning or replacement.4

How to diagnose

  1. Verify code origin and freeze-frame: confirm SPN 3719 FMI 16 is active/inactive, note engine hours, mileage, ambient conditions, and recent regen attempts from ACM/MCM data.
  2. Review regeneration history: check ACM logs for completed, aborted, or failed regens and driver key-off events during active regen; correlate with short-trip duty cycle.
  3. Inspect DPF differential pressure system: examine pressure sensor tubes for plugging, cracks, moisture or exhaust soot, and compare live DPF differential pressure (SPN 3251) at idle and at rated speed/load to expected ranges.
  4. Check aftertreatment temperatures: confirm DOC/DPF inlet/outlet temps reach and sustain regeneration thresholds during an commanded regen; look for temperature sensor rationality and heater/doser inhibit conditions.
  5. Assess engine-out soot contributors: review MCM data for EGR flow/target deviations, boost pressure vs. commanded, and injector performance indicators; address any accompanying engine faults before condemning the DPF.
  6. Evaluate ash service status: check service interval counters and historical ash-load codes (e.g., SPN 3720) to determine if ash loading is masking or compounding soot load; plan filter cleaning/replacement if ash service is due.
  7. Perform a controlled parked regeneration with diagnostic tool monitoring: observe soot-load model decrease, DPF differential pressure drop, and temperature profiles; if load does not decrease as expected, suspect sensor/input error or excessive soot production.
  8. Clear codes only after root cause correction and verify no recurrence under normal operation and a subsequent drive cycle that allows a complete regen.

Common mistake to avoid

Cleaning or replacing the DPF before checking its pressure sensor and tubes. Cracked, melted, plugged or wet sensor tubes, or a failing sensor, can set DPF codes while the filter itself is fine. They are cheap to check; clear and verify them before touching the filter. Source: FleetRabbit — P2002 DPF efficiency code causes and fixes.

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Scan-tool forced (parked) regeneration—0.5–1.5 hrsDIY with tools and a manual
EGR valve/passage carbon cleaning$20–$1001–4 hrsDIY with tools and a manual
DPF differential pressure sensor$80–$3000.5–1.5 hrsEasy DIY
DPF professional cleaning (bake and blow)$300–$7001–3 hrsShop

Typical US independent-shop figures; labor runs about $140–$200 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If a forced regeneration does not reduce calculated soot load, if DPF differential pressure remains abnormal after sensor/line service, or if accompanying engine faults (EGR, boost, injector) are present, have a certified Detroit technician perform full ACM/MCM analysis and emissions-system service. Do not service high-pressure fuel injection components without proper training and tools.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources

  1. Curated DTC seed — Detroit DD15 (curated) ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — Detroit DD15 (curated) ↩︎

  3. Curated DTC seed — Detroit DD15 (curated) ↩︎

  4. Curated DTC seed — Detroit DD15 (curated) ↩︎