A bunch of people on the bonneville forum use a relay with the CD or Cassette circuit inside the stock radio and a switch and line out (headphone jack) run into the center console. This way they can use both the CD/cass unit while still having the Aux Input on the radio. In the Pontiac Radios, to use the aux input, the CD or Cassette has to be “running” inorder for the unit to not throw an error code and revert back to radio.