Oldsmobile's traditional naming strategy is one of those things that kind of got lost to time -- even at GM itself. Traditionally, the first number in the Olds name referred to the car's size class; the "70" series was smaller than the "80," which was smaller than the "90." The second number referred to the number of cylinders. So, technically this model-year car should have been called the "Oldsmobile 86" But, tradition is usually cooler than technical accuracy, so GM could be forgiven for the slip.
The 3.8-liter V-6 used in this car was a derivative of the Buick 3.8-liter, which by this point had become GM's "corporate" 3800. While GM wasn't forced to switch to OBD-II computer controls until 1996, engines like the 3800 got the more sophisticated system a couple years early. Code P0321 is defined as "Ignition/Distributor Engine Speed Input Circuit Range/Performance." This engine doesn't have a traditional distributor, so in this case the code refers to a faulty crankshaft position sensor reading. That could mean a bad crankshaft position sensor, or it could indicate a lose sensor wire, corroded wire terminal connections or a problem with the wiring or the computer. Low charging-system voltage can also trigger this code. If this code is accompanied by a low-voltage code, the problem is likely the alternator or something else in the charging system. More than likely, though, it's a bad crankshaft position sensor.