High voltage oxygen sensor

I NEED HELP PLEASE.
I have a 2006 Chevrolet Aveo. When it's hot, the oxygen sensor voltage rises. The injectors and fuel pressure regulator have already been checked, and all the sensors are within excellent operating ranges.
The oxygen sensor and coolant temperature sensor have been replaced.
I tried a module from another car, and the problem persists. The canister purge valve was disconnected, and it's still the same.
When the engine reaches normal operating temperature, the scanner shows a closed loop, and intermittently the loop opens. At that precise moment, the long-range fuel regulation goes negative, dropping to -34, and the O2 sensor voltage starts to rise to 1300 mV.
Can anyone help me?

It would be good if you disconnected the oxygen sensor(s) while the problem is occurring to see what readings the scanner shows. They should be around 450 mV; if they rise, the problem is internal to the ECU.