I don't have a '94 so I don't know how much is changed. If you don't have a fuse that's labeled O2 sensor heater, then maybe it just uses the ECM fuse. If that fuse were blown the engine wouldn't run at all.

That leaves wiring... The wires running to the O2 sensor are down under the car, where they can be pulled or smashed while someone works on your exhaust.

The Helm manual says exactly which wire is which, so for example you check that one wire has +12v like it should - another wire needs to be properly connected to the ECM, etc...