Radio wiring problem 2001 Audi A3

you have a bad connection between head unit and rear window

2001 Mitsubishi Galant Car Stereo Radio Wiring Diagram
Car Radio Constant 12v+ Wire: Red/Black
Car Radio Switched 12v+ Wire: Blue
Car Radio Ground Wire: Chassis
Car Radio Illumination Wire: Green/White
Car Stereo Dimmer Wire: Black/Yellow
Car Stereo Antenna Trigger: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Front Speakers Size: N/A
Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): White/Blue
Left Front Speaker Negative Wire (-): Black/Blue
Right Front Speaker Positive Wire (+): White/Red
Right Front Speaker Negative Wire (-): Black/Red
Rear Speakers Size: N/A
Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Yellow/Blue
Left Rear Speaker Negative Wire (-): Gray/Blue
Right Rear Speaker Positive Wire (+): Yellow/Red
Right Rear Speaker Negative Wire (-): Gray/Red

Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Gray
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
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

Not sure I understand your question. Did you buy a harness adapter for GMC, or are you trying to just cut the connector off the factory radio and solder it to your CD player? If the latter, below is the color code for your factory wiring.

1994 GMC Sierra C1500 Car Radio Wiring Schematic
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: N/A
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

try connecting them to a small radio or tape player to see if they still work ?? if they appear to work ok on a small set then i would be inclined to check the colours on the speaker wires then rmove the radio and try connecting another known to be good speaker to the output on the radio and if that works ok then renew the feed wires to rear speakers because thats where your fault would lie for whatever reason like a mouse got in or seat crushed the wires or whatever

DOES THE RADIO PLAY? HERE ARE THE FACTORY WIRING COLORS FOR THE RADIO HARNESS, RECHECK YOUR WORK. IF U FIND NOTHING THEN IF THE RADIO PLAYS THE CD PLAYER IS DEFECTIVE, IT HAPPENS BELIEVE ME.

2001 Chrysler 300M Car Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Pink
Car Radio Accessory Switched 12v+ Wire: Red/White
Car Radio Ground Wire: Chassis or Strap
Car Radio Illumination Wire: N/A
Car Stereo Dimmer Wire: Orange
Car Stereo Antenna Trigger Wire: Orange/Red
Car Stereo Cell Phone Mute Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: Located under the rear deck in the trunk.
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Dark Green
Left Front Speaker Negative Wire (-): Brown/Red
Right Front Speaker Positive Wire (+): Violet
Right Front Speaker Negative Wire (-): Dark Blue/Red
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown/Yellow
Left Rear Speaker Negative Wire (-): Brown/Light Blue
Right Rear Speaker Positive Wire (+): Dark Blue/White
Right Rear Speaker Negative Wire (-): Dark Blue/Orange

Here is the diagram in words as found at

http://www.modifiedlife.com/2001-mazda-millenia-car-stereo-wiring-diagram/

Car Radio Battery Constant 12v+ Wire: Red/Black
Car Radio Accessory Switched 12v+ Wire: Blue
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Green/White
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: 5 1/4′
Car Audio Front Speakers Location: Doors
Left Front Speaker Positive Wire (+): Yellow
Left Front Speaker Negative Wire (-): Blue
Right Front Speaker Positive Wire (+): Pink
Right Front Speaker Negative Wire (-): Purple
Car Audio Rear Speakers Size: 6′ x 9′
Car Audio Rear Speakers Location: Rear Deck
Left Rear Speaker Positive Wire (+): Green
Left Rear Speaker Negative Wire (-): Yellow/Green
Right Rear Speaker Positive Wire (+): Green/Black
Right Rear Speaker Negative Wire (-): Green/Orange

Hello, I have a 2000 ES300 and while the body style is different believe the newer model still has the rear deck mounted sub-woofer that you are referring to. The process of removing this speaker would start off the same as if you were going to replace the third brake light also located in this housing. Using a flathead screwdriver work your way around prying/popping up all four corners of the speaker grill covering the speaker that have the retainer clips. Once you disengage the clips work/maneuver the grill up and towards you gently and it should slide out. The bulb for the third brae light will be attached to this speaker grill, disconnect the snap wire from the bulb and you should have a clear visual of the speaker and the four bolthead screws securing it. Remove these screws and your almost home free. The next part might be slightly more difficult. If the speaker s simply connected by a clipped on wiring harness, just detach.On my 2000 ES300 i have the pioneer system(Not Nakimichi) and the 2 wires (one black, and one red) are soldered directly to the speaker. You can take a soldering iron(maybe a battery or gas powered one unless you have an inverter) and remelt the solder to remove the wires or you can elect to simply cut the wires. If you choose to cut them make sure you cut them as close as possible to the soldered joints so you have plenty of wire left to install the replacement speaker.Then install replacement either soldering or using crimp clamps and reassemble. ( Note if you simply want to add a aftermarket amplified sub-woofer you don't need to remove the sub-woofer out of the housing. You can tap into the wire leads and run it directly to the amplifier. Just cut one of the wires leading to the stock sub-woofer so it doesn't also come on and potentially blow while the radio is on. This will also prevent any bass humming when the radio is shut off but the aftermarket amplifier is still on because once one of the wires to the stock sub-woofer is disconnected or cut it breaks the circuit. Hope this helps.

You need to attach the blue wire on the stereo harness to the blue and white wire on the car adapter harness. they installed a small amplifier to power the rear door speakers and unless you connect those two wires then the speakers will not work.

This is normal. I also have a 2000 ES300. This became a problem when i tried to run an aftermarket sub off of the wire leads from the stock sub-woofer. When I would switch the radio off there would be a loud, deep, constant bass tone. As far as I know you cannot stop the voltage from continuously supplying the sub-woofer this is the way the factory amplifier is programmed, however, if you cut one of the wires(youhave to cut because wires are soldered to sub-woofer) the humming noise will not occur when radio is shut off. Cut the wire in middle and add crimp connectors so you can reconnect later if needed. You only need to cut one and it doesn't matter whether it's the black or red wire.