po418 Secondary air relay

There are several posts about PO410 codes, but none about the PO418 code. The is "Secondary Air Injection System Relay A Malfunction. Does anyone know where this is located at. Thanks!!!

Update. I believe I might have found the relay. It is the one beside the battery & next to the pump fuses? It seems it would be. If anyone knows how to test is let me know. Thanks

I changed relays and still the code is present. I left the battery upplugged for 10 minutes which shold have cleared the code. Any suggestions???? Also my mileage seems to be poor also. I have a 2001 4x4 Blazer with the 4.3.