Did all 3 sensors throw the codes suddenly, and at the same time? If so, having all 3 go south simultaneously is rather rare. However, wiring issues common to these sensors could cause the problem, and given the age of the vehicle, a very likely problem. Not familiar with your vehicle, but if you could locate a wiring diagram, and see where the power and ground circuits to these 3 systems are common, and trace the wiring. On the older U bodies, the bulkhead connector for engine to body is a frequent source of problems such as this. Sometimes a quick way to find it was to wiggle, push, pull, squeeze the wiring bundle as the engine is running, and see if engine performance changes or CEL comes on. Be careful, however, of rotating parts as you do that.
Jeff