I replaced both rear O2 sensors about 2k miles ago. In the past week the CEL came on; checking the codes I get signal and heater errors for both rear sensors.
How likely is it that both of them failed at the exact same time? Or could there be another culprit?

 

Who manufactured the sensors? Where did you buy them? I had BOSCH sensors fail right out of the box on multiple occasions, all purchased via amazon.
I also recall that even though I was 99.5% sure I had really made sure the connectors clicked together, I found they had not. Worked find for a while but then stared tossing codes.

 

Actually, even though I was sure I had replaced the rear sensors when I look back at my order history it seems that I actually replaced the fronts. I know that people have had problems with the Bosch ones so I was going to go with Walkers.
I'm much less concerned now, except for the weirdness of both sensors going out at the exact same time.