I've had a check engine light on for a couple of weeks now. (95 Altima GXE) I had the car scanned, and 2 codes are persistantly coming up--EGR malfunction, and knock sensor. I cleaned out the EGR valve & hoses(the valve seems to be working just fine, but it is not getting pressure sent to it for some reason) As far as I can tell the Backpressure transducer (BPT) is also working fine. This morning I swapped out the EGR control solenoid for a junkyard part--this had no effect on the problem. What am I missing here? Thanks, Phil