The speed sensor is integral to the hub & bearing assembly. If it is bad, you have to change the assembly. First check that the connector is clean, tight and plugged in.
Seems to be a rather common DTC. It means that the rear air mix door is not exactly where it is commanded. In other words, it is commanded at 40 degrees open and it is reporting 42 degrees. I had the same code and the dealer tech told me that it does not take much variation to trip that code. Since I was having no problem with rear seat heat, I told them to leave it along even though it is still under warranty.