P0401 🟡 Moyen ✅ Can drive (carefully)

Exhaust Gas Recirculation (EGR) Flow Insufficient

The EGR valve is clogged with carbon deposits or stuck closed. Very common on diesel engines over 80,000 miles.

🚗 Common on: Diesel: VW, BMW, Ford, Vauxhall, Peugeot, Renault diesel

💷

Average repair cost

£12 — £350

🔍 Symptoms

  • → Check engine light on
  • → Black smoke on acceleration (diesel)
  • → Power loss / limp mode possible
  • → Rough idle

⚙️ Common Causes

  1. 1Clogged EGR valve (soot deposits — main cause on diesel)
  2. 2Blocked EGR cooler
  3. 3Faulty EGR position sensor

🔧 Recommended Fixes

  1. 1Clean EGR valve with EGR cleaner spray (~£12) — often sufficient
  2. 2Replace EGR valve (~£60-250)
  3. 3Check EGR cooler circuit

🛒 Recommended Parts (Amazon UK)

EGR valve cleaner spray~£10-12
View on Amazon UK →
Diesel EGR/DPF additive~£12
View on Amazon UK →
EGR valve replacement~£60-200
View on Amazon UK →

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Frequently Asked Questions

Can I clear this code without fixing it?

Yes, but it will return if the underlying issue isn't fixed. Clearing a code only tells you if the problem is permanent or intermittent.

Will this code fail an MOT?

Probably yes if the check engine light is on during the MOT. The MOT checks OBD readiness monitors since 2018.