Upgrading radio, question about antenna

Hello, I am replacing the stock head unit on my 2000 4Runner, probably with a Sony XAV-AX5000, or something similar, but I noticed that it only has one antenna input. When I took apart my dash to see what would fit, I found two antenna wires plugged into my factory head unit, one small and one large. I unplug the larger one, and loose reception for AM, FM still works. I unplug the smaller one, and loose reception reception for FM, AM still works, but I get more static and get a deep bass sound coming through every few seconds and the motorized antenna goes up and stays up, even when I power the car off.
I did a google search, and I always find that only the larger one needs to be plugged in, as its for the front antenna, and the smaller is for the rear, but in my case the reverse seems to be true. So, my question is would this work,

$17 Carxtc Diversity Antenna Harness Adapter When Installing a New Radio, Fits Toyota 4Runner that has two antenna connector plugs

https://www.amazon.com/Diversity-Antenna-Harness-Installing-connector/dp/B015X33YHO , so that the motorized antenna will still go up and down when I turn on my vehicle?

Thanks!

 

That means your stock head unit came with a Diversity radio tuner. They are phased out as of a long time ago. In most cases the big one is connected and the small one is left alone. I have a 2002 in which I am going to switch out the radio soon myself. You can always just hook up the big antenna connector to your new headunit and be OK. The only way to tell would be to try it out for a few days before casting judgement on if it's needed. It would be wise to take the testing method as I see that the adapter is $15 plus $15 shipping and it is not sold by or protected by Amazon so a refund might not happen.

 

Cool, thanks for the information. I'll try what you suggest.

 

I ran my first aftermarket radio in my 2001 4runner without that diversity antenna adapter and found there were quite a few stations I wouldn't pick up compared to the factory unit and the amount of static I started to get drove me nuts as well. When I upgraded again I purchased that adapter and have had zero problems since.