Don't compare the two downstream sensors to each other.
Compare each downstream sensor to its respective upstream sensor.
Your B1-S2 graph looks like an upstream sensor graph. That means the cat is dead. Upstream sensors should switch back and forth just like your B1S2 graph while at idle. The downstream sensor should change much more slowly as the cat processes the exhaust.
Dead cat. If in warranty, have the dealer replace it. Otherwise, consider the option above of gutting it or just installing MIL eliminators.
Steve
