Is there a specific first place to check like there is for a front door non working speaker?

 

If you own a multi-meter, take the speaker out and attach the speaker wires to each other. Pull the connector from the radio and check for continuity. If there is no continuity, use a length of wire to extend each speaker wire up to the front so you can test each wire for continuity to narrow down which one is broken. The wires in my 99 run from the radio into a harness under the floor door trim before finally going up at the trim near the hatch. You can see the wire harnesses at the back, top.

Todd