It looks like those units share both the ground and power to the amplifiers. So to test both of them. Pull one of the rear speakers, Look at the connector on it. It should have six wires.
The dark green with gray stripe will be the battery positive line. Use a test light connected to a good ground to see if you have power to it. If you do not then check fuse 14. If it is okay test the speaker relay in the power module next to that fuse. (just swap it with one of the others with the same number of pins)
If you have sound the relay is bad.
If no sound, find a good bare steel ground spot and connect it to the gray wire with a dark green stripe. If you now have sound you have a bad ground connection. You could just leave the wire you added in if you make a good connection to the wire.
If none of this restores the sound it could be a bad head unit as it is unlikely that all of the amplifiers would go out at once.
Images (Click to enlarge)
Tuesday, August 22nd, 2017 AT 10:30 PM