I own a 2007 HHR LS base model - no mods - completely stock except for aftermarket wheels.
Radio does not interest me so I usually listen to CDs. I pull into a convenience store, shut the engine off, lock the door. The CD was playing when I pulled in. I return to the car, start it , and the CD sounds muddy and distorted and sound is heard only out of one side. I cannot hear the turn signals blinking. I drive home with the CD turned off and open the car door with the key in the ignition and there is no chime. I take the key out, scratch my head, put the key back in and start the car. The radio, door chime and turn signal click all return to normal.

Any insight into this strange occurrence?

 

Software glitch, just like when your home PC locks up. When you restarted the vehilce it was like rebooting a PC.

Or your fuses are loose.

 

I had an issue were I would loss the sound in my radio, but at the same time I would loss the door chime and turn signal chime. After turning the vehicle off and then restarting it - everything worked (for a while). My dealership replaced the radio two times and was about to do it a third. They said thats what thier GM Troubleshooting book said to do. I contacted GM Assistance myself and finally got the issue resolved. I would suggest taking it to your dealer and having them check the "Body Control Module" looked at. That is what they had to replace on mine - thus far no issues. TTFN

 

Same problem but easy fix, fortunately. I turned the radio on and got audio, but only from the rear door speakers. Then they too slowly faded, despite my cranking up the volume. While indicator lights flashed (both outside and on dashboard) when I signaled a turn, I didn't get the "tick-tock" audio.

Solution? Tighten the fuse seating. Fuse box on HHR is under the hood on the driver's side in a compartment with a snap-on/off lid. Remove lid (snaps on both top & bottom) and check the diagram under the lid to find the fuse at position #56. Gently remove the fuse with long-nose pliers and hold it up against a light to see if the fuse is intact (i.e., not broken, or still "fused"). If it's good, firmly reseat the fuse (don't use too much pressure, but enough to make sure it's snugly in place). Before closing the fuse box, run your finger over other fuses to make sure they're all securely seated as well. I found a few that were a bit loose.

When I turned the key to "accessory" mode, all 4 radio speakers and the turn indicator audio worked again . I did have to try the turn signal indicators twice before the "tick-tock" sound returned. Your experience may vary.

IF YOUR FUSE IS BAD, you may find a spare replacement fuse mounted to the underside of the fuse box lid (gift from Chevrolet?). Make sure to select the proper replacement fuse (they're color-coded).

 

#56 fuse is interesting.
The manual labels it "Sensing and Diagnostic Module" (SDM).

 

Interesting indeed! My 2008's fuse box diagram corresponds to the 2005-6 diagram (I don't know why) where #56 is in the engine compartment and designated "Audio, OnStar." "Sensing and diagnostic" fuse is position #24 in the floor console fuse box.

Strange.

 

Evidently your diagram is NOT for an HHR since there was no 2005 model. My guess is that the fuse box or cover was replaced with a junkyard lid. The fuse fits many different cars.
I believe your result is coincidental probably opening ande closing the driver side door revived the speaker for a time.The chimes have nothing to do with XM/Sirius, OnStar or the optional amp. The radio HU sends the chimes to the front left door and tweeter speakers. If you have the Pioneer system with the amp & sub woofer the chime tone does go through the amp on it's way to the door, but that would cut out all sound.

 

I'm taking my info from a 2010 manual. And #56 is in the engine fuse box.
My OnStar fuse is in the car #24.

 

That is correct on all years and models HHR I can find. Underhood #56 is SDM on the BCM #24 is XM/OnStar #13 is SDM.

 

Who knows?

My radio is original, basic Chevy equipment, not an optional brand (such as Pioneer). The fault affected the radio speakers only, not the radio -- that tuned in stations just fine -- and the audible "tick-tock" of the turn signal indicator. The "2005-06" fuse diagram I mentioned in an earlier post meant the 2006 model (I believe it first went on sale in 2005).

So I guess the bottom line is check your model's fuse diagram for where the audio fuse is, then check to make sure it's not blown and/or is properly seated.