Diesel Trouble Codes

P0402 — Exhaust Gas Recirculation Flow Excessive (6.4 Power Stroke)

Diagnostic reference for 6.4L Power Stroke 2008-2010.

Updated September 2, 2026

What it means

Measured EGR flow is higher than commanded on the 6.4L Power Stroke. The PCM detects excessive EGR flow via EGR valve position/feedback and associated sensors. This platform has an EGR valve plus an EGR cooler; flow/position codes include P0401 insufficient, P0402 excessive, P0404 range/performance, P042E stuck open.12

Most likely causes

  1. EGR valve stuck open or mechanically binding — Valve fails to close, or carbon buildup holds valve off seat, causing continuous EGR flow. On 6.4L, EGR valve plus EGR cooler is present; P042E is defined as EGR control stuck open.2
  2. EGR valve position sensor / feedback error — Faulty position sensor or wiring reports incorrect valve position, leading PCM to see flow higher than commanded. P0404 is EGR control circuit range/performance on this platform.3
  3. EGR cooler bypass valve performance issue — Ford defines P2457 for this engine family as EGR cooler bypass valve performance, not generic EGR flow low. A malfunctioning bypass can alter effective EGR flow.4
  4. Carbon buildup / clogged EGR passages causing flow miscalculation — Excessive deposits in EGR passages or cooler can disturb flow characteristics, contributing to P0401/P0402/P0404 family on 6.4L.513

How to diagnose

  1. Verify code and freeze frame; confirm P0402 is present on 6.4L Power Stroke 2008-2010 with EGR valve + cooler.
  2. Inspect EGR valve operation and position feedback; check for sticking open or binding consistent with P042E stuck open definition.
  3. Check EGR cooler bypass valve performance per Ford definition for this engine family.
  4. Inspect EGR passages, cooler, and valve for carbon buildup that affects flow measurement; correlate with P0401/P0404 behavior.
  5. Review related EGR codes P0401, P0404, P042E for pattern; platform facts list these as EGR flow/position codes.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and shop; EGR valve, cooler, and labor can be significant on 6.4L. Obtain quotes from qualified diesel technicians.

When to see a pro

EGR diagnosis on a 6.4L Power Stroke involves high-temperature exhaust components and emissions controls. If you are not experienced with diesel emissions systems, have a qualified diesel technician perform diagnosis and repairs.

Sources

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

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

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

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

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

Watch a repair

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

2016 Ford 6.7L (P0402) — BL Automotive · 47K views

2019 6.7 Powerstroke EGR Maintenance: The Problem With Carbon Build-Up — Dave's Auto Center · 170K views

Ford EGR Flow Testing (P0401, P0402, P0405) — ScannerDanner · 699K views