Where is the radio amplifier on a 2008 GMC

Does the system have an amplifier ?
Circuit/System Verification
Radio ON, Rear Seat Audio (RSA) OFF (if equipped), adjust the fade and balance controls on the radio to test all four channels individually. Each of the four channels should produce clear and even sound.
Without Amplifier Radio ON, verify clear audio is heard from each audio speaker.
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If audio is inoperative from all speakers, replace the radio.

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If audio is inoperative from one or more, but not all, speakers or the audio emitted from the speakers is not clear, refer to Speaker Circuit Malfunction - without Amplifier.
With Amplifier Radio ON, verify clear audio is heard from each audio speaker.
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If audio is inoperative from all speakers, refer to Amplifier Circuit Malfunction.

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If audio is inoperative from one or more, but not all, speakers or the audio emitted from the speakers is not clear, refer to Speaker Circuit Malfunction - with Amplifier.

Circuit/System Testing
Speaker Circuit Malfunction - without Amplifier

1. Ignition OFF, disconnect the harness connector at the appropriate speaker.
2. Radio ON, test for 5.0-7.5 volts between the signal circuit terminal A and ground.
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If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.



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If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.


3. Test for 5.0-7.5 volts between the signal circuit terminal B and ground.
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If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio.



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If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.


4. If all circuits test normal, replace the speaker.

Bad amplifier. It's located in dash behind headlight switch. Happens often on these.

1st check fuse for Amplifier.

2nd if fuse is good, most likely the Amp has died. Common for GMC

My personal suggestion would be to go for these repair catalogs from
www.reliable-store.com instead. much better info on all vehicles, complete details, and they also have live assistance feature

i would check tightness of battery cables ,also the wires that go to the alternator good luck

If it has a premium sound system some of them have a small amplifier for the over all system and the rear out put may have lost signal out put power.If it does not have an amplifier then I would replace the head unit(deck)with a brand that you like so you have total control,and no that does not sound right.Hope this helps

not sure which radio you have but there is an amplifier under the back seat and there are some fuses there you may want to check your owners manual for fuse information

Here ya go. enjoy!
2002 GMC Sierra C1500 Car Radio Wire Color Codes
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: Brown
Car Stereo Dimmer Wire: Gray
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: Under the center console.
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue