P0401 - EGR Flow Insufficient on 97 Corolla

[Adee]

I posted just minutes ago and it seem to have disappeared.

Anyway, My mom's Corolla can't pass Smog Check here in California because of the Engine Light, it's throwing an Error Code of P0401 - EGR Flow Insufficient. I've reset the ECU then had him try again and it failed again, did some search on the Internet and read that it can be 3 things, EGR Valve, Hose and Switch. Some people have replace this and still has the same problem. So was wondering if any of you guys might have a better idea.

Thanks