P0492 Volkswagen -

Question

2003 Passat V6.

Can anybody explain me how Motronic Engine Control Module throws P0492 code? I didn't find any sensor that could give the ECM any input information on conditions of the secondary air injection system. Does it compute some indirect data like the output of the O2 Sensors?

As far as I understand, if I get constantly P0492 but never P0491 codes, the AIR (secondary air) Pump and AIR solenoid valve N112 operate properly, and the reason of the problem is somewhere in the the Bank 2 AIR branch: Combi-Valve. But I might be wrong with my assumptions.