Service Engine Soon on Olds Ciera

I was told about this problem when I purchased the car..The previous owner claimed that after he installed a new battery he didn't reset the computer and the Service Engine Soon light started coming on after he did this, but never had before.

The light comes on quite frequently, almost at regular intervals it seems.

Assuming this is true any tips on how reset the computer?

disconnect the negative battery terminal for 10 minutes. reconnect and start engine with all systems turned off. let it idle up to normal operating temperature

otherwise if it is not true what the former owner told you
I had that light come on for a long time, took it in and they replaced oxygen sensor and light quit coming on. I dont know if it always means it is oxygen sensor (presuming it is not just some other fault like you mentioned). I think it threw out a code when they ran it on the computer at the service station