Help Me Diagnose Audio Issue

So this is not in a Toyota product of any kind. It's a 2001 Chevy Silverado. I have totally replaced the audio system in the truck and the subwoofer ain't woofing. I'm using this five-channel amplifier: Reference 7005A | High performance 5 channel car amplifier (infinityspeakers.com) The front and rear channels are working fine. But I getting nothing from the subwoofer channel. I've checked wiring as much as I can without tools. And nothing. I'm using this headunit: https://jensenmobile.com/cm901mir.html. The headunit is very simple and there's very little in the way of settings. At any rate, I've played with the any subwoofer-related settings and still nothing.

The sub is DVC 4ohm and it's wired in series inside the enclosure.

Don't need in-depth troubleshooting yet. I ordered a tone-generator thing to test stuff. I'm leaning toward a bad channel in the headunit or a setting I missed. The owner's manuals for these things are crap. How can you include a three-page manual with audio components??

If/when the tone generator narrows down the problem, I'll be shooting off emails. Just looking to see if someone has knowledge of something I may have missed. Thanks!

 

Maybe verify all three 30A fuses are good.

You can move Front or Rear RCAs to the Subwoofer input on the amplifier for the purpose of testing that amplifier channel since you know you have signal on those pairs.

I’m also wondering why you have your sub wired to 8 ohms since that amplifier is 2 ohm stable on the sub channel.

 

Did verify the fuses are good. And the RCA relocation is something that was a "d'oh" moment later in the day. I've made a note of it for sure. I was attempting to diagnose in between breaks from mowing the lawn.

And whoops! I meant parallel for the sub wiring. Coffee hadn't taken effect yet.

Thanks for your reply!