I think what this refers to is simply a oxy sensor, imo
This P0470 code relates to an "egr boost sensor failure"
This is what the disk/manual I have, says to check for it:
improper harness connection
improper or damaged hoses
open/short in harness (EGRB, EGR CHK, SIG RTN, VREF, VPWR)
* examine EGR boost sensor and EGR boost check solenoid vehicle harness
* examine EGR boost sensor and EGR boost check solenoid hoses and hose
As I recall, screwed right on top of the egr valve, is a sensor with a 3 wire plug going into it.
When the egr valve operates (not unlike a radio speaker, but operating from a vacuum signal), the pin protruding from the bottom of this sensor picks up that valve movement, and sends info back to the ecm, imo.
I don't have a picture I can send you right now cause my car is stored off site...anybody?