Diesel Trouble Codes

P0401 — Exhaust Gas Recirculation Flow Insufficient (6.7 Cummins (EGR + DPF, pre-SCR))

Exhaust Gas Recirculation Flow Insufficient

Updated September 2, 2026

What it means

Measured EGR flow is lower than commanded on the 6.7 Cummins 2007.5-2012 EGR+DPF pre-SCR platform.1

Most likely causes

  1. EGR valve stuck closed or restricted by carbon/soot — EGR valve fails to open or is blocked, so actual flow is below commanded. Typical on 6.7 Cummins 2007.5-2012 EGR+DPF pre-SCR.1
  2. EGR cooler internal blockage or external restriction — Cooler passages clogged, limiting flow to the intake. Typical on this platform.1
  3. EGR flow measurement discrepancy due to intake or exhaust restriction — Upstream/downstream restrictions can make measured flow appear low relative to command.1
  4. EGR control circuit / actuator performance issue — Control circuit range/performance fault can cause insufficient flow.2
  5. EGR valve stuck open causing adaptive compensation — Stuck-open condition can lead to control adaptations that result in insufficient flow under certain conditions.3

How to diagnose

  1. Verify freeze frame and repeat the fault under steady cruise conditions.
  2. Inspect EGR valve operation and carbon buildup; check valve movement and seat condition.
  3. Inspect EGR cooler for internal blockage and external leaks.
  4. Check EGR position sensor/actuator feedback and related wiring for faults.
  5. Review EGR commanded vs actual flow data and intake/exhaust restriction indicators.
  6. Confirm no related EGR control circuit range/performance codes.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and severity; obtain local quotes.

When to see a pro

If high-pressure fuel system work is suspected or safety-critical systems are involved, have a qualified diesel technician diagnose and repair.

Sources

  1. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎

  3. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎

Watch a repair

Third-party videos, not ours — for illustration. Confirm anything against the factory service information for your truck.

6.7 FORD P0401 FIX egr cooler replacement — In The Shop · 144K views

P0401 on the 6.7 Powerstroke — DieselTechRon · 179K views

6.7 Ford Diesel |Repair YOUR P0401!!!| The right way!!! — PowerStroke Tech Talk w/ARod · 128K views