P0400 EGR Flow
What does P0400 mean?
P0400 — EGR Flow. This is an OBD-II diagnostic trouble code a scanner retrieves when your vehicle's computer detects egr flow. The level of risk depends on how the vehicle is currently running and how long you've been driving with the light on.
Common causes of P0400
- Carbon-blocked EGR passages
- Failed EGR valve stuck closed
- Faulty EGR position sensor
- Blocked EGR tube or port
- EGR vacuum or control solenoid failure
How to fix P0400
- Read EGR desired vs actual position with a scan tool
- Command the EGR open and watch the pintle respond
- Inspect and clean the EGR passages and valve
- Check the EGR tube for blockage
- Replace the valve or clean passages and retest EGR flow