P0400: Exhaust Gas Recirculation (EGR) Flow Malfunction
The EGR system isn't flowing correctly, either too much or too little.
Green, yellow, red: three ways P0400 can look
The same code can be a quick fix or a reason to pull over. Match your situation to the closest example.
Keep an eye on it
Drives normally.
Schedule a repair
Rough idle or pinging. Get it serviced.
Stop and get help
Stalling or heavy knocking. Stop and get help.
Symptoms you might notice
- Rough idle
- Pinging
- Hesitation
Common causes, cheapest first
- Clogged EGR valve or passages
- Failed EGR valve
- Sensor problem
What you can check before calling
- Note rough idle or pinging
A code points to a system, not a part. Replacing parts based on the code alone is how people spend money without fixing the problem. Testing confirms the cause first.
Generic codes (second character 0) mean the same thing on every vehicle. Some manufacturers add their own details, so check service information for your exact vehicle.
Related codes
More egr codes
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does P0400 mean?
P0400 means "Exhaust Gas Recirculation (EGR) Flow Malfunction". The EGR system isn't flowing correctly, either too much or too little.
Can I drive with code P0400?
It depends on what the vehicle is doing. Green: Drives normally. Yellow: Rough idle or pinging. Get it serviced. Red: Stalling or heavy knocking. Stop and get help.
What causes P0400?
The most common causes are: clogged EGR valve or passages; failed EGR valve; sensor problem.
Is P0400 a serious code?
It can be. Stalling or heavy knocking. Stop and get help.
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