Carbon-clogged EGR valve. Faulty EGR valve. Blocked EGR passages or cooler. EGR position sensor fault. Vacuum supply issue to EGR.

Which cars are affected by P0400?

P0400 is most commonly reported on Vauxhall, Ford, Volkswagen, Renault, Peugeot vehicles, but can appear on any make.

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P0400

Medium severity

Exhaust Gas Recirculation (EGR) Flow Malfunction

The EGR system is not functioning as expected. The ECM has detected that the EGR flow does not match what was commanded, either too much or too little recirculation.

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Common causes of P0400

1Carbon-clogged EGR valve

2Faulty EGR valve

3Blocked EGR passages or cooler

+2 more causes

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Commonly affected vehicles

VauxhallFordVolkswagenRenaultPeugeot

P0400 can appear on any vehicle — these are the makes where it is most frequently reported.

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Related fault codes

P0171Medium

System Too Lean (Bank 1)

P0300High

Random/Multiple Cylinder Misfire Detected

P0420Medium

Catalyst System Efficiency Below Threshold (Bank 1)

P0172Medium

System Too Rich (Bank 1)