[Jeff2KPatriotBlue]

It is not clear to me what you are describing.

When you say "all wheel drive came on", do you mean the warning light?

The problem with fuel economy is not solved by turning the light off, but by fixing the problem with the AWD system that is triggering the light.

 

[Jeff2KPatriotBlue]

Is it a "part time" AWD system? I had assumed it was "full time".

 

[Jeff2KPatriotBlue]

If it depends on a temp input, and that Input is bad, it will likely act up.