One problem related to crankshaft position sensor has been reported for the 1999 Buick Century. The most recently reported issues are listed below.
While driving vehicle (1999 gm Buick Century ,120,000 miles) on at least 10 different occasions in the past 2 years the vehicle engine has stalled and all electrical power is lost. This has happened on the freeway while driving at 70 mph, it has happened on city streets at 45 mph. After the vehicle stops it can be restarted. There are no warning indicators displayed before or after. Initially the check engine light did not come on and there were no code diagnostics indicating a problem. The vehicle has been serviced 3 times. The gas cap, crank sensor have been replaced and the computer reflashed. The vehicle now maintains a constant small evap leak warning code and the check engine light is always on although the service mechanics cannot find any associated leak problem and the car drives perfect except for the intermittent and sudden engine stall and sudden loss of all electrical power . The vehicle has stalled on 2 occasions since the last service encounter. My internet searches indicate this is a big problem that few Buick owners have been able to resolve for many years. I think the sudden loss of engine power and electrical power for steering, brakes, lights at any speed without warning warrants investigation. When this occurs at night on the road - suddenly no one can see you stopped in the middle of the road.