According to and obdii guide, this is for the Secondary AIR System, bank 2.

I was reading somewhere that this could be caused by the passenger side check valve which has carbon buildup and that it's a $15 part at Napa.

Has anyone changed one of these or can anyone give me more insight?

 

Been there, done that. GM PN is 12565503

 

I wasn't finding much on google, and totally forgot about the search function on here

Looks like it's a cheap part. I hope this is it! I just bought a house and the last thing I need is for my car to start having trouble.

 

That should do it, or you can try cleaning it first. If you don't reset the code the light will go off by itself after a few cold starts without a failure, but stay in memory for a while.

 

How do I know if it fixed it?

I read somewhere that if it's a pending code, it takes 40 cycles/starts to reset, but elsewhere I read that if it's fixed, the light will go out immediately.

After I clean/replace the valve, is there anything short of resetting the pcm and hoping the SES light stays out to let me know it's fixed?

(lol...I guess I want my car to thank me and just tell me it's satisfied!)