P0400 Exhaust Gas Recirculation Flow
The EGR system flow is not as expected.
Common causes
- Carbon-clogged EGR valve or passages
- Faulty EGR valve
- Vacuum or wiring problem
Symptoms
- Check engine light
- Rough idle
- Pinging under load
What to check
- Inspect EGR valve and passages for carbon
- Command the valve with a scan tool
- Check vacuum lines
Manufacturers may add their own detail to generic codes. If your vehicle shows a different description for P0400, follow the service information for that make and model.