Diesel Trouble Codes

EGR Flow Problems — Detroit DD15

Diagnostic guide for EGR flow problems on Detroit DD15 (2010–present).

Updated October 15, 2026

What’s going on

EGR flow problems on the DD15 mean the engine is not achieving the commanded cooled-EGR mass flow. The MCM/ACM/CPC compares EGR valve position and delta-pressure feedback to a target; a mismatch sets EGR flow target errors and can increase engine-out soot, which loads the DPF faster.1

Most likely causes

  1. EGR valve sticking or sooted — Carbon buildup or varnish can cause the EGR valve to stick open or closed, producing an EGR mass flow rate above or below target. This commonly sets SPN 2659 FMI 0 (high flow) or SPN 2659 FMI 1 (low flow).123
  2. Restricted EGR cooler — Internal soot or coolant-side restriction reduces EGR flow, leading to low-flow target errors such as SPN 2659 FMI 1 and faster DPF loading.13
  3. EGR delta pressure sensor or sensing lines fault — A faulty delta-pressure sensor or plugged/ leaking sense lines gives incorrect flow feedback, causing the controller to report EGR flow target errors (SPN 2659 FMI 0 or FMI 1).123
  4. DPF soot load increase from EGR faults — EGR flow errors raise engine-out soot, which can raise calculated DPF soot load and set SPN 3719 FMI 16.14

How to narrow it down

  1. Read stored and active codes from the MCM and ACM with a Detroit diagnostic tool; note SPN 2659 FMI 0, SPN 2659 FMI 1, and SPN 3719 FMI 16.
  2. Review freeze-frame data for engine speed, load, coolant temperature and EGR commanded vs actual flow at the time of the fault.
  3. Inspect EGR valve operation and cleanliness; check for carbon buildup, binding, or actuator response using the diagnostic tool’s actuator test.
  4. Inspect EGR cooler for external leaks and internal restriction; verify coolant flow and temperature differential across the cooler.
  5. Check EGR delta pressure sensor and both sense lines for damage, plugging, moisture or leaks; compare sensor output to a known-good reference under steady conditions.
  6. Inspect intake and exhaust piping for leaks that affect EGR pressure differential; verify turbo boost and intake air system integrity.
  7. If SPN 3719 FMI 16 is present, evaluate recent regeneration history and DPF differential pressure to confirm whether increased soot is from EGR-related engine-out emissions.
  8. Clear codes, perform a road test with live EGR flow, valve position and delta-pressure data, and confirm the fault does not return.

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
EGR position/temperature/differential pressure sensor$60–$3000.5–1.5 hrsDIY with tools and a manual
EGR cooler$1,000–$2,5006–10 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 the EGR valve requires removal, the EGR cooler needs internal service, or high-pressure fuel systems are involved, have a qualified Detroit technician perform the work. Do not attempt repairs on high-pressure fuel injection systems. If the vehicle enters a derate or shows SCR/DEF faults, address those with a professional as they can lead to operator inducement.

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 symptom 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) ↩︎