Step 2 - Service Area
WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
There are great differences in the sizes of the service area for AM and FM monaural. Sometimes FM stereo broadcasts cannot be received even though AM comes in very clearly.
FM stereo has the smallest service area, and it also picks up static and other types of interference ("noise") easily.