2000 code P0410 manlfunction

I have a 2000 blazer with 140,000 miles on it. The service engine light came on a couple days ago. I had the code read but I am not sure what to do next. He code is P0410- secondary air injection system malfunction. Does anyone have any suggestions on what to check for this code?

Thanks for any help you may give me.
Ray

Your first step in diagnosing is to know if the the air pump is activating. You can actually hear this from the drivers seat. Also check the vacuum lines for cracks.