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2004-2006 AUDI A8
4.2L V8•AWD•AUTOMATIC•gas•BAS
3 active safety recalls on this vehicle — view recalls
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Repairs0Labor488Torque2164Fluid10DTC1049Battery1Maintenance0Recalls3
P0401moderate severityPowertrain

EGR Flow Insufficient Detected

on 2004-2006 Audi A8 4.2L V8 · AWD

What this code means

The EGR system is not flowing enough exhaust gas. This is one of the most common EGR codes.

Symptoms

  • Check Engine Light
  • Pinging under load
  • Failed emissions (high NOx)
  • Slight rough idle

Common causes

  • Clogged EGR passages (most common)
  • EGR valve stuck closed
  • Clogged EGR tube
  • Faulty DPFE/MAP sensor
  • Carbon buildup in intake manifold

Diagnostic steps

  1. Check EGR passages for carbon restriction
  2. Test EGR valve by applying vacuum (should open and idle should change)
  3. Inspect EGR tube between exhaust and valve
  4. Test DPFE sensor (Ford) or EGR position sensor
  5. Clean carbon from intake ports

Repair notes

Clean EGR passages and valve. This is maintenance, not just a repair. Replace EGR valve if cleaning fails.

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