Where is the auxiliary audio input jack in a 2000 grand am?

Most, if not all, of these radio do NOT have an aux input. After market car audio shops will have a device that will plug into the antenna jack so that you can tune in your MP3 player via the radio.

This antenna adapter has much better reception than the average FM Transmitter.

FM is one idea but the sound quality is not that good, there is nothing better than

digital audio directly into the Pontiac radio preamp

Most Pontiac radios come with a source or aux button this is for the external CD changer or auxiliary audio input. If you look on the back side of the radio there is a free 9 pin plug you need a GM9-AUX

search on any search engine for

Pontiac Auxiliary Input Converters