my check engine light was on so i got it checked at autozone and got code p0401. the egr valve seems to work ,i did the vacum hose test. i checked the egr passages at the valve and the throttle body. what else can it be? i had reset the ecu after checking the stuff and drove for like a half hour and got no check engine light. than i turned the car off started it back up and in a little while it came back on. any suggestions. is there a way to test the DPFE ?
