Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
There has been a service bulletin for that type of concern. Here is what it states.
Bulletin No.: 07-08-44-008
Date: April 18, 2007
with Speakers, Premium Audio w/Amplifier or Rear Stereo Audio (RPOs UQA, UQS or UK6)
Some customers may comment on one or all of the following conditions related to no audio/no sound:
No sound from one or more of the radio speakers.
No blinking sound heard form the turn signals or hazard signals when on.
No audio warning chimes heard when a door or liftgate is opened.
The C2 Audio Amplifier Connector may become unseated at the amplifier.
Inspect/Seat the C2 Audio Amplifier Connector (16-way, Black Connector).
Remove the radio, amplifier, and SIR fuses located in the Underhood Bussed Electrical Center (BEC).
Visually inspect and pull on the C2 Audio Amplifier Connector (1).
If the connector is properly seated, then refer to SI for further diagnosis based on the customers condition.
If the connector is loose, then reinstall the C2 Audio Amplifier Connector.
Verify the connector is seated and locked into place.
Install the fuses.
Verify the condition has been fixed and clear any DTCs.
If securing the connector does not correct the condition, refer to SI for further diagnosis and repair.
Install the radio speaker amplifier assembly and any other components removed to gain access to the amplifier. Refer to Radio Speaker Amplifier Replacement in SI.