While stopped at a red light the oil light came.

I dnt know saab all that well but it the oil light comes on its a few things ur low on oil or u have no oil or low oil pressure wich means the block could be cracked or a seal could be gone or theirs a leak in the system some where wich would lead to a loss of oil wich then leads to a siezed engine. Did u hear any ticking comming from the engine befor this happend