I found a PI, Preliminary information on this issue. It has some steps to follow.
#PIT3522F: Buzz Noise From Rear Speakers After Bulletin 04-08-44-014B - keywords AMP amplifier door radio sound speaker UQA - (Sep 17, 2008)
Buzz Noise From Rear Speakers After Bulletin 04-08-44-014B
2004-2007 Buick Rainier
2004-2009 Chevrolet TrailBlazer models
2004-2009 GMC Envoy models
2004 Oldsmobile Bravada
2005-2009 Saab 97x
This PI was superseded to update model years. Please discard PIT3522E.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Rear speaker noise on vehicles with rear seat audio controls (RSA) and Bose amplifier. This noise can be produced from a variety of high load or PWM controlled electrical components (rear window defroster, heated seats...) but usually can be identified as an whine noise related to engine speed (generator electrical feedback). This condition can be verified by turning the RSA on (rear speakers off) and the noise should go away. If the noise is the same the root cause most likely exists elsewhere and additional diagnosis is necessary.
Perform the following procedure to reduce the rear speaker buzz noise AFTER all low level and high level circuit integrity has been verified. For example, it is possible for the system to produce audio output to the speakers even if a (-) circuit has an open. However it will most likely produce undesirable noise in this condition.
Note: Bulletin 04-08-44-014B applies to 2004-2005 vehicles only. The Transfer Case Control Module ground has been relocated on all 2006 and newer vehicles. The information may be helpful on 2006 and newer vehicles.
Important: Prior to moving forward with the directions below, all 2008 model schematics refer to all connectors as the letter "X" followed by the connector number. The letter X is the new global term for connector. Since this PI address 2008 and prior, the connector number will be written both with the letter C and the letter X.
Note: After each step below, re-evaluate the concern. If the concern is repaired, there is no need to continue with additional steps.
- Check for damaged harness under the passenger rear 2nd row seat. This step applies to short wheel base vehicles ONLY equipped with AMP RPO UQA.
- Remove the passenger side second row seat.
- Remove right rear sill plate
- Lift carpet and follow body harness as it travels along the passenger rear second row seat toward the amplifier.
- Repair any damaged wires and reroute the harness to prevent future concerns.
- Remove the AMP connector. On short wheel base vehicles, the AMP is located behind the right rear 1/4 trim panel. Removal of the trim is needed to access the AMP. On extended wheel base vehicles, the AMP is located on the left rear 1/4 trim panel. Remove the access panel in the left rear trim and locate the AMP connector.
- Remove the C1 or X1 AMP connector.
- Disconnect and pin drag terminals B3 B4 B5 B6 and B12. Use test probe J-35616-6 (BN). Replace any loose or damaged terminals as needed.
- Reinstall the AMP connector and evaluate.
- Inspect the Bare Wires for terminal Integrity.
- Remove the radio and the C1 or X1 connector.
- Check terminal tension on C1 or X1 terminal A5. Use test probe J-35616-6 (BN). Replace any loose or damaged terminals as needed.
- Remove the AMP connector C1 or X1 and C2 or X2
- Check terminal tension on C1 or X1 terminal B12. Use test probe J-35616-6 (BN). Replace any loose or damaged terminals as needed.
- Check terminal tension on C2 or X2 terminal E. Use test probe J-35616-6 (BN). Replace any loose or damaged terminals as needed.
- Remove the center console assembly from the vehicle. Refer to the Console Replacement procedure in the Instrument Panel and Console sub-section of the service manual.
- Locate the C307 or X307 connector to the left of the transmission tunnel. The driver's seat may also need to be removed in order to gain access.
- Inspect the connector and see if it is fully seated. Secure connection as needed.
- Unplug the connection and pin drag B1 B2 B5 and B6. Use test probe J-35616-4A (PU). Replace any loose or damaged terminals as needed.
- Locate the C304 or X304 connector. This is located under the second row rear seat on the driver's side. There is a cut out in the carpet where this connector can be accessed.
- Inspect the connector and be sure it is fully seated.
- Disconnect the connector and pin drag terminals D3 D6 D7 and C12. Use test probe J-35616-2A (GY). Replace any loose or damaged terminals as needed.