G
Guest
Hi I had the service engine light come on in my 2001 4.6l expedition. I used my diagnostic computer on it and it came up p0401. I reset the computer and then the light came on again and I checked it and it came up p0402. I know that the codes have to do with the egr system but i dont understand why it would go from insuficient flow to excessive. If anyone has any ideas on what it could be please help me out.
