CEL on got the problem, now need help Options

[97celiman]

so i threw a CEL P401 soooo here are the 6 things it could be

EGR valve stuck closed
open or short in VSV circuit for EGR
Vacuum or EGR hose disconnected
MAP sensor
EGR VSV open or closed malfunction
ECM

What is ECM and VSV?

i can check the hoses and like a dirty MAP sensor (can i have a dirty EGR valve hence the closed?)

i know you have to clean with non corrosive stuff (no brake cleaner) what does anyone recommend?

how do i know when its fixed, i know you can disconnect battery to reset computer and get rid of CEL or does the CEL go away after its fixed then disconnect to reset.

Any thoughts appreciated.

[97celiman]

so now the light will turn on and off. not rapidly, one day it will be on and one day it wont...very annoying. the car seems to be running fine so i am very confused.