check engiine light

I have a 1993 Buick Regal GS. My check engine light comes on from time to time. I pulled the code and it said it was the o2 sensor. I replaced it and it still does it. The light only comes on when the rpm's are at the same speed for a extended period of time ie: cruse control or highway. As soon as I hit the gas hard or even brake it will go away. Any suggestions would be good

Could be a loose connection. But I'd check with a dealer to be sure. I hate idiot lights!

Maybe the O2 sensor isn't bad, only it has a bad reading like when the engine is running too lean or too rich, I suggest you to check the air filter, spark plugs, and look for a vacuum leak.
I've a 1981 monte carlo that has the same problem with check engine light, at constant speed it turns on, it is the speed sensor and TCC..