The CEL is off because the code was erased.

I may be wrong but if the CEL is off it was turned off by someone or the reguired number of "clean starts" was met........about 30-42 starts.

That code pertains to the EGR valve diaphram sumpt'n,sumpt'n....book is out in the truck.
My 00 turns that code on every other month or so.I just turn it off and drive.
It normally happens after driving for a long time a set speed,then slowing down fast and stopping....ie; off interstate,down ramp,into gas station,
Rodeo off............get gas.......start truck,pull out
get back on interstate and ***** CEL.

My .02 is I would just drive it.........

Bansil