Failed emissions test... help
Reply #13 –
The computer controls the EGR by "dithering" the control solenoid. It applies pulses to the solenoid to either suck some more air out and open the EGR a bit more, or let a little air bleed back in so the valve closes a bit.
Don't take this drawing as gospel, even though it shows green to the EGR valve. I just used the different colors to separate the functions and make it easier to follow.