I understand that the voltage on the pre-cat O2 sensor must cross 0.5V (by a 0.3V margin). Is it also the case that the voltage on the post-cat sensor must cross 0.5V? The following image clarifies my question.
As these two graphs show, the post-cat barely crosses 0.6V; it doesn't cross 0.5V. Is this an indication of a faulty post-cat O2 sensor?