P0400 fault code-feedback signal incorrect.4 wire sensor. Power and ground good. I can command valve open, duty cycle changes and valve opens, but feedback duty cycle stays the same, have plugged in new whaler egr and feedback is the same as old unit. I expected to see a change in feedback signal as the valve opens.i suspect faulty part but what are the chances of two valves having the same internal fault.one other possibility I am thinking is wrong part supplied, even though it looks perfect.please help