Aftermarket radio on but no sound?

It might be defective, here are the radio wiring diagrams so you can double check the installation and see how the system works. I did notice there is an amplifier so the aftermarket radio must be compatible and if not, you will need to wire the speakers up individually. Check out the images (below). Please let us know how it goes.

To bypass the amp or? Did the aftermarket radio come with instructions for this? If you want to bypass the amp use the wiring diagrams to connect to the speakers.

You will need to search for a radio that has this capability or wire the speakers directly at the amp using the wiring diagrams I have provided.