OBD · Emissions control
P0400 Exhaust gas recirculation flow
What this code means
P0400 is a generic OBD code shared by all manufacturers since 2001 for petrol and 2004 for diesel. It relates to: emissions control. The code tells you what the ECU measured as abnormal, not necessarily which part to replace.
Most common causes
- Clogged EGR valve#1
Cost of related repairs
| Independent garage | Main dealer | |
|---|---|---|
| EGR valve | £275 – £740 | £360 – £1,145 |
How to read this code
An OBD scanner plugged into the 16-pin socket under the steering wheel reads and clears codes. Bluetooth models cost £20 to £40. Clearing a code without fixing the fault is pointless: it comes back.
Related problems
Frequently asked questions
What does code P0400 mean?
P0400: Exhaust gas recirculation flow. P0400 is a generic OBD code shared by all manufacturers since 2001 for petrol and 2004 for diesel. It relates to: emissions control. The code tells you what the ECU measured as abnormal, not necessarily which part to replace.
Can I drive with code P0400?
Monitor. You can drive normally but get it checked in the coming weeks. It may fail an MOT or roadworthiness test.
How much does it cost to fix P0400?
EGR valve: £275 – £740.
How to read this code
An OBD scanner plugged into the 16-pin socket under the steering wheel reads and clears codes. Bluetooth models cost £20 to £40. Clearing a code without fixing the fault is pointless: it comes back.