P0400: Exhaust gas recirculation (EGR) flow

What does it mean?

System

Powertrain (engine and transmission)

Subsystem

Emissions (EGR, catalyst, particulate filter, vapours)

Type of code

Generic code: means the same on every make.

How urgent?

Have it checked soon. You can usually still drive, but avoid long trips and heavy loads.

Possible causes

• Dirty or sticking EGR valve (carbon build-up)
• Blocked EGR cooler or passages
• EGR valve position sensor or connector
• Vacuum hose or pressure converter (on a vacuum-operated valve)

Tip: don’t just clear the code. Clearing a code doesn’t fix the cause. It often comes back, and the stored data that helps us find the cause is then gone.