Diesel Trouble Codes

P0404 — Exhaust Gas Recirculation Control Circuit Range/Performance (6.4 Power Stroke)

Diagnostic reference for 6.4L Power Stroke 2008-2010. Platform facts are authoritative.

Updated September 2, 2026

What it means

The engine control module has detected that the exhaust gas recirculation control circuit is operating outside its expected range or performance. On the 6.4L Power Stroke 2008-2010, EGR hardware is an EGR valve plus an EGR cooler.1

Most likely causes

  1. EGR valve position feedback / control circuit fault — The PCM commands the EGR valve and compares actual position to expected. A range/performance fault indicates the valve position sensor signal or control circuit is out of expected range.1
  2. EGR valve sticking or mechanically binding — Carbon buildup or a failing valve can cause the valve to stick, resulting in position vs. command mismatch and a range/performance set.1
  3. EGR cooler bypass valve performance issue — The 6.4 EGR system includes a cooler bypass valve. A performance fault in the bypass valve can affect overall EGR control and contribute to range/performance codes.2
  4. Wiring / connector / reference voltage issue to EGR valve or position sensor — Open, short, corrosion, or reference-voltage problems in the EGR control circuit will cause the PCM to see an out-of-range signal.1
  5. EGR cooler-related flow restriction or internal leak affecting control — The EGR cooler is a known failure point on this platform. Cooler issues can alter EGR flow characteristics and influence control performance.1

How to diagnose

  1. Verify freeze frame and confirm P0404 is present with no other EGR-related codes that would point to a different root cause.
  2. Inspect EGR valve electrical connector for corrosion, pin damage, and secure seating; check wiring harness for chafing, heat damage, and continuity to PCM.
  3. Command EGR valve position with a scan tool and monitor commanded vs. actual position PID; look for lag, non-linearity, or inability to reach commanded position.
  4. Check EGR valve reference voltage and position sensor signal voltage sweep during manual valve movement; compare to expected range.
  5. Inspect EGR valve pintle and passages for carbon buildup, sticking, or damage; check valve moves freely without binding.
  6. Evaluate EGR cooler bypass valve operation and related circuits; on this platform the bypass valve performance is monitored separately and can influence EGR control.
  7. Review recent regen history and EGT sensor data; excessive soot loading or cooler restriction can affect EGR flow control.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and shop. EGR valve replacement, wiring repair, or EGR cooler service can be costly on the 6.4 platform. Obtain a written estimate before authorizing work.

When to see a pro

If the valve is seized, the EGR cooler shows signs of coolant intrusion, or wiring faults require harness repair, have a qualified diesel technician perform diagnosis and repair. Do not attempt high-pressure fuel or emissions-system repairs without proper training and equipment.

Sources

  1. Curated DTC seed — 6.4 Power Stroke (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 6.4 Power Stroke (curated) ↩︎