I have a 2004 sonata v6. The stock radio was a double din. It powered on and all functions seemed to work but no sound. I replaced with an aftermarket stereo and same result. I checked the radio Amp fuse under dash and Amp fuses under the hood. All are good. Located the stock Amp in the trunk and think that's my issue but not sure. Fuse is good on it. How can I test to ensure this Amp is in fact the issue before buying one? Thanks to anyone who knows!

 

Did you make sure the wiring to the speakers is not open somewhere and if so how did you check them?

Because there are altered connections with the changes, you may need to have a radio shop check that.

If you don't have the test equip to do the tests , you can't get very far.
What kind of test equip do you have to use?