So the code I had flashing was 04-13

WTF?

The decoder doesn't even have an option for 13 short pulses.

 

Reset the ecu and see if it comes back.

 

From haynes repair manual

0413 Upstream oxygen sensor circuit slow response fault (left bank)

 

What's that mean for me? Code did go away when I reset.

 

I had the same code issue for the right bank O2 sensor. I put in a new sensor but I don't think that was the problem since I've gotten the code again and I tested the sensor to make sure it was good.
There are a few different things that can cause that failure apparently according to the FSM. I haven't quite figured it out yet.

-exhaust leak
-fuel pressure
-injectors
-air intake leak
-Mass airflow sensor

There is a whole list of things to check out. See how long it takes for the code to come back. It's possible that it was just an intermittent failure.