Diesel Trouble Codes

P0401 — Exhaust Gas Recirculation Flow Insufficient (6.7 Power Stroke)

Diagnostic reference for P0401 on 6.7 Powerstroke.

Updated September 1, 2026

What it means

Measured EGR flow is lower than commanded.1

Most likely causes

  1. Carbon-clogged EGR valve or cooler — Typical on this platform: carbon-clogged EGR valve or cooler.12
  2. Failed EGR valve motor — Typical on this platform: failed EGR valve motor.1
  3. EGR position sensor / valve assembly rationality fault — EGR position feedback implausible versus command can contribute to flow insufficient detection.3

How to diagnose

  1. Verify code P0401 is present and check for related EGR codes such as P046C.
  2. Inspect EGR system for carbon clogging of valve or cooler; NHTSA report notes obstructed EGR cooler cord causing exhaust fumes and check engine light on 2011 F-250.
  3. Check EGR valve operation and motor function; typical causes include carbon-clogged valve/cooler or failed valve motor.
  4. Evaluate EGR position sensor feedback rationality versus command.

Parts and tools you may need

Rough cost and difficulty

Cost varies by root cause and labor; diagnosis only.

When to see a pro

If diagnosis indicates internal EGR component service or high-pressure fuel/exhaust work, have a qualified diesel technician perform repairs. Do not perform step-by-step repair of safety-critical systems.

Sources

  1. Curated DTC seed — 6.7 Powerstroke (curated) ↩︎ ↩︎ ↩︎

  2. NHTSA owner report 10510437 ↩︎

  3. Curated DTC seed — 6.7 Powerstroke (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

P0401 on the 6.7 Powerstroke — DieselTechRon