Engine light stays on

I had the secondary air pump replaced and a week later the engine light came back on. I bought a Actron scanner ($250.00) because these garages charge &100.00 or more just to tell me what is wrong. Could it be the "air injector shut off check valve)? Or could it be fuses or plugged lines? Most importantly where is the secondary air injector shut off check valve located? I/m thinking it may be the valve up against the fire wall. Thank you