Where is the butterfly valve when checking for back pressure i have a po475 code

Question

I also have these codes 344,478,470

Answer 1

P0475 Exhaust pressure control valve malfunction

P0344 Camshaft position sensor circuit malfunction

P0478 Exhaust pressure control valve high input

The main problem that you have is a P0344 , unless you like to stall out every where you ignore this code. The fix for P0344 is replace the CMP sensor. P0478  check the turbo if there is any missing bolt replace it. getting to the exhaust pressure control valve you remove the turbo charger compressor manifold, just sight the solenoid and make sure the connection are intact.

here the back pressure solenoid, correct for P0344 first.