Easiest way to Troubleshoot Sub RCA Outputs / Cables?

I'm certain there's a million ways to skin this cat, but I've currently got a Sound Ordinance powered sub under my drivers seat that recently dropped all sound output. Just wanted some input on the easiest way to figure what's up. Here's what I've got going on:

Power to sub appears to be good, power light comes on, and both the inline fuse from battery and the internal fuse on sub are good when checked for continuity w/ volt meter.

Sub remote turn-on signal appears to be fine, sub turns on as expected with key in accessory position.

I just wanted to see what are the easiest ways to troubleshoot both the RCA cables and the sub output RCA jacks on the head unit? It's a Pioneer AVH-3700BHS if it matters.

Any insight is appreciated - Thanks

Mike