What could be next thing cause EGR system fail.? Code p 401. on 1997 Toyota Camry

I checked EGR valve ,replaced EGR modulator and vaccum switch valve.
But engime light still on after running for couple miles.Some one know about this give me advice what is the possible part cause this problem.Thanks e.

1 answer
The things that need to be checked and items that can cause this code are listed.
Engine Control Module (ECM)
Restricted Exhaust Gas Recirculation (EGR) Passages
Dirty Throttle Body
Vacuum Modulator
Vacuum Switching Valve