What is the reason for the P0400 Exhaust Gas Recirculation Flow Malfunction?

[LeElisa]

When the exhaust valve is damaged, it cannot control the amount of exhaust gas recirculation. Below is a detailed introduction to the related content: Damaged exhaust valve: When the exhaust valve is damaged, it cannot control the amount of exhaust gas recirculation. Excessive exhaust gas participating in recirculation will affect the ignition and performance of the air-fuel mixture, thereby impacting the engine's power output. Especially during engine idling, low speed, small load, and when the engine is cold, the recirculated exhaust gas will significantly affect engine performance, triggering an engine alert. Therefore, users should replace the exhaust gas recirculation valve. Hazards of a damaged exhaust valve: A damaged exhaust valve can cause the car to burn oil, with severe blue smoke from the tailpipe. The reason is that the exhaust valve also functions as an oil-gas separator. When working properly, it only draws in exhaust gas and not oil. When the exhaust valve is damaged and loses its oil-gas separation function, it draws in oil along with the gas, allowing oil to enter the intake manifold and combustion chamber, resulting in oil burning and severe blue smoke from the tailpipe.