I think you got your OnStar button inside your car stuck
You outta gas? Do you got a flat?

from Eminem – Same Song & Dance Lyrics on Rap Genius

Meaning

OnStar (made in Detroit) is a service that some cars have. By pushing a button you get connected to an OnStar operator that can assist you with various things (tell you how to quick-fix something in the car, call a towing service, give you directions… )
Tonya’s car broke down, and Eminem is pondering what happened.

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