The 2005 Pontiac Grand Am's factory stereo is not equipped to accept external stereo components. To connect an external device you will need to first establish an auxiliary input. Use an FM modulator to make the AUX connection to the factory stereo deck. You can choose to have the AUX line installed professionally or you can purchase the FM modulator and adapters to make the connection yourself for a fraction of the cost.
Lift the Pontiac's hood and remove the grounding cable from the battery. Loosen the bolt on the cable with a wrench. The grounding cable connects the negative battery terminal to the frame of the Grand Am. Lift the cable from the battery and set it aside. Move to the inside of the vehicle.
Pry the panel that surrounds the Grand Am's stereo and climate controls away from the dashboard with a trim panel removal tool. Set the panel aside. Remove the two screw bolts at either side of the stereo deck with a 9/32-inch socket and drive. Slide the stereo from the Pontiac's stereo dock and disconnect the stereo wiring cable from the back of the unit.
Plug the wiring harness adapter lead connectors into the outlets on the FM modulator. The FM modulator will be used as the AUX input, providing a hard-wired connection to the factory stereo. Connect the FM modulator's wiring connectors to the corresponding outlets on the rear panel of the stock head unit.
Stow the FM modulator in the back of the Pontiac's stereo dock. Feed the FM modulator's input cable into the glove compartment adjacent to the stereo mounting dock. Slide the stereo back into the dashboard and replace the two screws on the side of the unit. Replace the dash panel and press firmly around the panel's edges to snap it back into place.
Open the glove compartment and position the FM modulator's input lead for easy access. Return to the Grand Am's engine compartment.
Replace the grounding cable's clamp over the negative battery terminal post. Tighten the bolt on the cable with the wrench and close the Pontiac's hood.
