CentralCoaster wrote:
Hmm. I guess EGR should only affect Nox. But resetting the ECM will affect idle and everything else.

Does your EGR temp switch and circuit work? It should ground only when hot and EGR is flowing.

It can throw a code if its shorted/grounded. Probably also if it doesn't ground out when it's supposed to be flowing, which sounds like your situation. The sole purpose of that switch is to throw codes.