As per title what would be considered as correct pre cat o2 and post cat o2 voltage at operating temperature and idle? My pre cat o2 stays around 1.5V and post cat o2 0.5V.

 

What year is the car? What engine?

 

Hey I just looked it up in Mitchcell1.

 

It is Mini Cooper S R56 2007 with N14.

 

I am using Delphi Ds150e tool to monitor voltage of the o2.
I am confused how it works as I was told that the voltage of pre cat o2 should jump around between 0-0.9V when engine is hot avaraging to 0.45V.
Then other guy told me that pre cat o2 is wideband and when engine is hot it should be up to 3V.
Could someone explain what should be the value when everything is working correctly?

 

What you were told is true for a narrow-band O2 sensor (should cycle between .2 and .8 volts). MINI uses a wideband O2 sensor (upstream). On systems with a wide-band sensor, the engine computer (DME) uses a measurement of the electrical current sent to the pump cell inside the sensor to adjust fuel trim not voltage to the Nernst cell. Systems with wide-band sensors are a lot more sophisticated; if a sensor goes bad, the DME will tell you.

If you have the time, watch this video from Wells.

 

Thank you for explanation @mkov608