OBD2 code P0412 what is the problem ? Where do I look for the problem?

P0412 is related to the Secondary Air System. This code is common in BMW's from 1996 - 2005. During cold starts, the secondary air system pumps fresh air into the exhaust allowing for a more complete burn of hydrocarbons (harmful emissions). The secondary air system only operates during a cold start, is audible (you can hear the pump running) and turns off after a minute or less.