1996 Chevy Cavalier engine light

A 96 Cavalier has 2 oxygen sensors, a single wire in the exhaust manifold and a 4 wire (heated) just after the catalytic converter.
Check the wiring to see if it is broken. Check for damage to the sensor itself.
Chances are the heater circuit in the sensor is bad.
With that many miles, replacing them wouldn't be a bad idea anyways. Also check all fuses.
What the heater does is preheats the sensor so it will tell the pcm to lean out the fuel mixture sooner for better efficiency.
Unfortunately, with a check engine lite on, you won't pass a smog test.
Hope I've been a help. If so, a vote of confidence would be nice.

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VIC