So I want to preface I looked at the other posts and used search feature and couldn't find my exact problem. So a couple of years ago my uncle installed an aftermarket radio on my HHR 2010 LT 2.2L , It worked well for many years however it starting acting up and my guess is the internal radio amp gave up eventually. It would sound muffled and then randomly kick in and work eventually it sounded muffled all the time.

So I bought an aftermarket radio on Amazon this one: (Nilight Fuse Holder Add-a-circuit Fuse TAP Adapter Mini ATM APM Blade Fuse) well that didn't work, because I needed a fuse slot that not only was on in Accessory mode aka turn off when car is off/ key is out of on position, but also powered the radio. Well I tried various fuse slots nothing worked it was always the same thing .

Then i tried a new aftermarket wire harness from red wolf (RED WOLF Radio Wiring Harness w/Antenna Adapter Compatible with 2006-2013 GM GMC Sierra Chevy Impala Buick Cadillac Install Aftermarket Stereo CD Player Receiver Wire Cable Adapter) I checked and it said it fit 2006-2011 HHR cars and well now my audio completely gone. It turns on and got the accessory to work but no sound not even the radio or Bluetooth.

So then I figured cheap radio for $50 you get what you pay for so I bought a new radio the (PLZ 7" Wireless Double Din Car Stereo Apple Carplay Radio Screen for Car Audio Receivers) for $100. Same thing got the radio on but no audio but this time it's different now the BCM module is getting backfeed I think because my car's security lock dash light is on and on some fuse slots it prevents car from turning on, also the dash light go on the fritz like turn on and off and then the high beems go on autom and then i hear the clicking noise for the sevurity lock dash light. However the moment I remove the fuse tap car goes back to normal.

Might be related Car issue:
Also it might not be related but about a week ago I finally fixed my emergency light button it was damaged and I replaced the housing of the button. I disconnected everything from the panel, the airbag light, the traction button, the dimmer, the cigarette lighter, the back window wiper button, emergency button. Well When I went to put it back I got the traction button wrong with another plug that looked identical but had a different color well it made my traction control not work so then I took the panel off again and put the right plug in and well it works again, the problem is ever since i removed the dimmer switch the dimmer doesn't work the lights don't go up or down in brightness, the gear selector lights are off and only a few lights on the climate control turn on but the symbols are are off on the ac vent selector. Also the dash lights don't change brightness no more with the dimmer, it works because when i turn all the way to the right the cabin lights all turn on but the rest doesn't work.


At my wit's end been trying to figure it out because I want to fix it, not a radio tech. I like learning but it seems I keep getting more and more away from my goal. any advice is appreciated.

 

As you might have seen in other radio threads , Crutchfield.com has the correct modules to connect the aftermarket radio to your HHR , in there they will ask you if your HHR has the 6 speaker factory system or the premium upgraded Pioneer 7 speaker system. The aftermarket parts you purchased may fit but they aren’t compatible.

 

I couldn't make it to the end. Any of the "unused" fuse positions on the BCM (inside fuse box) are switched. The stock radio only has a always on 12 volt input and a digital switch to turn it on and off; therefore you need a switched source and a always on source for an after market, or a digital adapter.
The speakers are the most common failure point.
You probably blew a fuse on the BCM. Many people are unaware of the inside fuse box, on the passenger side of the console below the radio.

You can get a FREE Owner Manual via the link in my sig.

 

I've been doing my fuse tests on the BCM module by the passenger side. However after a day of researching it would seem I need data interface harness to connect my aftermarket radio. Still I'm unsure how the previous aftermarket radio was able to work but these new ones weren't.

 

Yup. After I kept looking I stumbled upon this video.

(Chevy HHR CarPlay/AA Stereo Upgrade | Step-by-Step DIY Guide)

Pretty much telling me what you mentioned.

I was going to get this: (Heise Axxess Gm Data Interface 2006-2012)

However your recommendation have been spot on so I will be going with this one:
https://www.crutchfield.com/p_120AXD...e.html?tp=2977
(Axxess AXDI-GMLN11 Wiring Interface)

I have spent more money and soo much more time than if I just went to a shop and got the radio installed. However I want to learn and I suppose this is the price for it.

 

I thought I explained that.
The interface uses the digital (computer) signal from the BCM to turn the radio on. You can accomplish the same thing by having an always hot and a switched source that after market radios require.
All of the unused fuse positions on the BCM are switched and on the RAP relay.
You would probably save yourself a lot of time by looking at the links in my sig, FREE Shop and Owner manuals are available. Cars made this century use digital circuitry, not analog.