The air pump system is emissions related and if not working properly will set codes in the ECM (Engine Control Module) and turn on the "Check Engine Light". The Air Pump is part of a system called the Pulsed Secondary Air Injection System (PAIR). The three codes that can be set are; EFI-442 PAIR flow fault, EFI-446 valve leakage, EFI-448 pump flow too high. The EFI-442 is always set with either of the other two codes. When any of these codes are set, fuel trim is disabled.
When you start your car and it is cold, the air pump will start and run for up to two minutes. The Air pump is forcing fresh air into the exhaust to heat up the catalytic converter faster, rather like blowing on a fire. The air pump helps the car to get into emissions specifications faster. The system includes the Air Pump, SAS valve (secondary air system), and the Controller. The Controller is located just under the plastic where the word controller is in the above picture. The Controller receives open and close commands from the Engine Control Module (ECM). When the Controller is opened, vacuum from the intake manifold is applied to the purple vacuum line that routes back to the SAS valve. When the purple line on the SAS valve has vacuum, it will open and allow discharge from the Air Pump to be routed to the exhaust. The Air pump (located just below the battery and forward) is turned on when the Controller is opened. Should the SAS valve stick open because of exhaust gunk building up on the valve, moisture from the exhaust will find its way down to the air pump and eventually fill the Air Pump and Air pump relay with water, causing failure. On a positive note the SAS valve has been changed to open and close better, without sticking open due to engine exhaust. 1996-1997 systems have a relay (for the Air Pump) attached to the air pump frame; in 1998 the relay was moved to the relay box just aft of the air filter box. When undertaking the repair, install a new SAS valve with gasket, Air Pump and relay. When buying the parts make sure you also get the clamps. Sometimes the water in the Air Pump doesn't destroy the relay and it can be used with the new Air Pump.
It doesn't matter which item you replace first, it is nice if the engine is not hot when you are replacing the SAS valve. These pictures are of a non-turbo, however the difference is minimal. To replace the SAS valve you will need a pair of dykes to cut off the clamps on the discharge from the Air Pump hose. The valve is held in place by two 10mm bolts on the under side of the valve. A small stubby 10mm works well to get the bolts out. On a turbo the bolts are very difficult to get out, especially the forward one. Once you have broken the bolts loose, they can normally be unscrewed by hand. I usually take out the bolts and then cut the clamp on the big hose. The purple vacuum line can usually be wiggled off with out having to cut the clamp. The clamps have a special tool to crimp them shut, but if you are careful you can use a pair of dykes to squeeze them tight. Once the valve is removed, install the new green gasket, install the hoses, and then screw in the 10mm bolts. On some of the "Turbos" I have found the discharge hose so hard and brittle that it just falls apart when trying to get it off the SAS valve; if you have this problem you will need to replace the hose as well. You can't cut off the brittle part and then try to work the hose on the valve; it will not fit. The hose can be routed down to the pump fairly easy if you remove the air filter box.
The above picture gives you an idea of what it looks like with the SAS valve removed and ready to install the new gasket and valve.
Notice that the 10mm bolts are not that big, don't tighten them too much or they can break off, and tapping them out is a real pain.
The replacement of the Air Pump and relay can be done from under the car as well as the way I am describing; I prefer going in from the top. You will be removing the battery from the car so make sure you have your radio code so you can get your radio working after you re-connect the battery. If you don't have the radio code, then stop by a Volvo dealer and they can get the code for you; for security reasons it is not given out over the phone. A 10mm wrench will allow you to disconnect the positive and negative cables from the battery. There is a plastic fastener that holds the battery in place on the bottom inboard side that fastens to the battery tray. Remove the fastener and slide the battery inboard and then lift it out of the car.
The battery tray is held in place with two 12mm bolts, remove them, and also a 10mm bolt that holds the positive cable in place to the tray. Once the bolts are out, slide the tray inboard to work it out of the fender. There are two rubber grommets that the tray slides into on the inboard fender. If they come out with the tray, take them off and put them back into the holes in the fender.
Once the tray is free of the fender, rotate it over so you can unplug the electrical connection to the cruise control vacuum pump as well as the vacuum line that attaches to the pump. Remove the tray and set it out of the way.
With the battery tray removed, you now have a good look at the Air Pump and the bracket that holds it to the car. The two bolts that hold the bracket to the car are 12mm, remove them.
With the 12mm bolts out you can maneuver the Air Pump and bracket to a position similar to the above picture so you can cut the clamps that hold the hoses to the pump. The large hose is the input and the smaller hose is the discharge. The Pump is more than likely filled with water, so it is a good idea to take the caps that are on the new pump and have them handy to put over the inlet and outlet when you remove the hoses.
Once the hoses are off the pump you can bring the pump up further so that you can begin to disconnect the wiring to the pump. There are two wire holders in place, you can release them from the frame by using a small set of needle nose to pinch the connection on the back and it will come unclipped from the frame. The wiring has a small black wire that is grounded to the car; undo the 10mm bolt that holds the blue battery ground and black Air Pump ground to the car. One the clips is not attached to the frame; you need to open the tie-wrap enough to slide the small black grounding wire out of both clips. The ground is going to come out with the Air Pump. Note that on the 1998 there is no black grounding wire to remove and no relay attached to the frame, just a connector for the pump.
Once the black ground wire has been removed from the wiring harness you can now un-plug the two left connectors in the picture that are plugged into the relay.
With the pump out of the car you will now have to remove the bracket and relay. Unplug the connector in the relay and then remove the three 10mm nuts that hold the bracket to the standoffs on the pump. Once the bracket is off, you need to remove the standoffs from the pump. The standoffs are 16mm, but with the rubber on them, a 17mm wrench works to break them loose to unscrew them.
With the bracket, standoffs, and relay removed, you are now ready to attach the new pump to the bracket. Install the standoffs (17mm), and then the bracket (10mm nuts), and the new relay. Assembly in reverse order applies. Before securing the clamps on the hoses, make sure the hoses will not twist when you slide the pump back into place, especially the discharge hose. Don't forget to plug in the power to the cruise control pump and attach the vacuum line to the pump as well. While the battery tray is out, it is a good time to inspect the vacuum line to the cruise control pump, especially where it routes under the battery; this is where they tend to crack and break.