This is a 1997 850T 4dr sedan. I noticed recently that sound eminating from the engine compartment was louder than usual. Upon opening the hood it sounds like something else is running in addition to the engine. I turned the engine off. Later while parked with the engine off I turned the ignition switch enough to be able to turn on the radio. The sound in the engine compartment started up again. It sounds like a small motor or even the windshield washer pump. It seems to come from the lower right front of the engine.

I stopped off at an AutoZone store and they ran a diagnostic check. The error code was 4-1-0 and described the malfunction to exist in the secondary air injection system. That fault is not listed in the Haynes manual. I checked one of the repair shops and they thought it might be the air pump. Another mechanic told me there is no air pump in a turbo. The Haynes manual specifically mentions not having any information on air pumps (the information was not ready at the time the manual was printed).

Please respond if you have any idea of what is going on and if you can pinpoint the problem what the repair cost estimate might be.