I have an 1997 850, and my check engine light came on. I had it diagnosed and the code was P0410 secondary air intake malfunction. well I checked all hoses,wires leading into the air intake hose and found no deteriorated lines what else could this be.
It usually doesn't cause an issue driving, but you could fail emissions. It would probably cost you in the range of $400 - $600 USD to fix. You'll probably need a new air pump and valve. The valve probably isn't working and allowing water to go into the pump causing the code.
If possible, activate the air pump to make sure it works. Like sulley07 said, you may have water in the air pump, so new pump, valve, and vacuum nipple is required. If the pump works, then try and new valve and nipple