Have a look at www.kolbenschmidt.de/en/index.php?fidz301004 this tells you what the secondary air injection is all about. Basically under certain operating conditions (cold start) it blows cold air from the air box (so the air is filtered) into the exhaust manifold. This reduces emissions.

The above web address should lead you to a technical note for the the Pierberg secondary air blower (I have on my 850 AWD yours may be the same).

The air blower on my car is located under the battery - you have to remove the battery and then the plastic support panel beneath it. It is an enclosed electric motor with an enclosed fan all in one unit. There is are two hoses, one to supply clean air from the air box, one to pump the air to the exhaust manifold.

My pump is full of water. Note sure why. I think I will need to speak to Volvo. The water has leaked into the motor and it no longer works. I have replaced the pump and motor but it still fills with water. The water source is condensation from exhaust gas. I think the one way valve on the exhaust manifold is faulty.

Note not sure about your error code - I can't read mine, apparently I need a special tool that costs about £1,000.