Hi,

I was getting an occasional P0400 EGR flow error even after replacing EGR valve from a working car. After recently replacing the exhaust manifolds and working with the EGR system, I knew that it was hooked up right and should be good, but it still threw a fresh P0400 code. I was also hearing a regular a knocking tapping sound, which I hoped was the old manifolds, but it was still there after replacing them.

I decided to take a look at the EGR Temperature Sensor and found it was really caked with carbon, see the pics
After cleaning with a wire brush I cleared the code and started the car. It was instantly much quieter and idled with barely a wobble on the steering wheel. Before you could really feel the engine idling,
I have driven around 100 miles since this and the car drives so much smoother and the engine seems a lot quieter than it did before. So far without a P0400 code

I couldn't find much on the sensor, so I thought I should share my experience in the hope it helps.


EGR Temp Sensor before

After cleaning with a wire brush