Exhaust Gas Recirculation Flow Malfunction
Verified1 source
1 source
- Official data (NHTSA)official_feed
What P0400 means
Caution — monitor closely
The EGR system flow is outside its expected range.
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General information, not a diagnosis or repair instruction. Always confirm with a qualified mechanic for your specific vehicle.
Common causes
- Exhaust Gas Recirculation Flow Malfunction
What to check first
- Inspect EGR valve for carbon buildup
- Test EGR valve operation with a scan tool
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