It's no good what you did there. Select just the 'Lambda 1 signal (Pre-Cat.)' and 'Lambda 1 signal (After-Cat.)' then go to 'Graph' menu and press 'Start', with the engine running of course. Then press 'Stop' when the graph screen is full. That will show you how things are. You need to have a graphic kind of like this in my photo.
If you have bad values, replacing the sensors won't make any difference. You need to fix what's causing the bad values. You only need to replace the Oxygen sensors when they don't send no signal or when their heating circuit it's broken. When that happens, ECU tells you, there'll be stored errors about it.
The Pre-Cat. Oxygen sensors should oscillate between 0.05 - 0.8 volts regularly (about every 1 second) at idle in a good running engine.
The Post-Cat. Oxigen sensor should oscillate as the pre-cat sensor, regularly but with less amplitude. When the air-fuel mixture is perfect, the O2 voltage value is exactly 0.45 V. So in a healthy engine the after-cat O2 sensor oscillates about between 0.4 - 0.5 V.
