Question 1

What does P0400 mean?

Accepted Answer

P0400 - EGR Flow Malfunction. The EGR system is not flowing as expected.

Question 2

What are the symptoms of P0400?

Accepted Answer

Check engine light, Possible rough idle, Slightly increased emissions

Question 3

What causes P0400?

Accepted Answer

Clogged EGR valve (carbon), Failed EGR valve, EGR passages clogged, Faulty EGR position sensor, Vacuum supply issue

Question 4

How much does it cost to fix P0400?

Accepted Answer

Typical repair cost: $100-$500. Remove and clean the EGR valve and passages — often fixes it for free.

P0400 — EGR Flow Malfunction

Don't guess — diagnose P0400 the right way