Hi SierraGal,
I am rather new here and I do not know how it works too. There is no scale, just that you can give maximum of what you have with minimum of 1, hope I am not wrong. Anyway nevermind about that, just glad to know I have been of assistance.
Too bad your car is out of warranty. If you are into DIY, there is an MPCS check connector behind the driver's fuse box which you can bridge to find any error codes. I do not know if the data that I have is relevant to your vehicle so no promise that it will work.