Since I have seen a trend developing with members complaining about the in-dash CD player stop working here is a cheap fix:
If the disk cleaner trick does not work then buy a used HU identical with the one you have (all you care is to have a functional CD player, don’t look for scratches, cracks and such). Expect to pay between $20 and $60.
Since the ’98 and newer HUs are Theftlock enabled, you can not just swap the HU, you need to connect a Tech II scan tool to clear the VIN from the newly installed unit. This can cost anything between $0 to $100 (average price $50) and usually the Tech II scan tool (fairly expensive piece of equipment) is found at GM dealers. Some dealers offer this service as a courtesy for the returning customers (good luck finding one). To avoid paying the fee you can use the original HU but replace the CD player module. You can replace ANY part of the HU as long as you keep the motherboard.
Here is how:
1) Having the HU removed from the car remove both the top and bottom covers (there is one single screw in the back of the unit near the bottom lip for the bottom cover (see yellow circle in the next picture) and one on the top right side for the top cover. Then observe the blue arrow, these are points where the cover is pressed against the case. The cover will be lifted as the violet arrows show (from the rear side).
2) With the covers removed disconnect the white banner cable shown in the picture below.
The cable is visible once the top cover of the HU is removed (down on the right side of the CD player module). Using your fingers (here is where you need to have long thin fingers) lift the left and right side of the connector (the upper side of the connector will lift releasing the banner cable). The top part of the connector just need to be lifted about 1 mm not removed completely.
3) Pull the Volume knob out (will come out relatively easily) and remove the small round sponge underneath. Then you can access the washer holding the switch in place. With a set of long nose pliers remove the nut and the washer.
4) Remove the HU fascia. In the picture below you can see 2 of the 5 clips holding the fascia attached. 2 on top one on one side and 2 on the other side. Caution they can break easily (the design is better than ‘96-’97 units but still). I found a safe way is to cut some small 18 AWG sections of wires (as seen in the picture below) and with a flat blade tool slowly lift the clips and insert the wires underneath using the wire as a shim. Once all 5 clips are lifted up (with the shim wires) using the same flat blade tool start releasing clip by clip (starting with the top ones) and the fascia should separate. I have never broken one clip with the wire shim trick.
5) The CD player module is highlighted red in the picture below. It is held in place by the four screws highlighted with yellow on the next two pictures. Two on the backside of the HU and two on the front side (under the CD slot) hence why the fascia needs to be removed.
Also it is attached to the HU motherboard with a small cable witch you need to disconnect in order to have-it removed.
Follow the reverse instructions to assemble everything back.
