Removing battery terminals and putting them back after a minute or so is known as "trying to reset ECU" but may not solve your problem. A better way is to get ECU reset by OBD.
I don't think you O2 sensor is giving the problem, with 20k on odometer it is noy likely to give away.
Think of the wires and parts that included in your car's service and you'll find the answer. For example, the plug socket is a long black plastic thing and it contains a coil in it, when it is tightened with excessive force the plastic part cracks and current jumps (this is a very common workshop error).
Please do not over speed your (keep it 100 kmph or bellow) car while engine check light is on. Use google for details