Here is the Owner's Manual for your Pioneer Radio
. If you look at pages 24 and 25 of the manual (section 4 which is part of the installation instructions), you will see that the wire intended to activate the remote amplifier(s) is also a blue/white wire from the Pioneer radio. So, assuming that the orange wire in your motorhome's wiring harness connects to the remote amplifier activation wire(s) the blue/white wire from the Pioneer should be crimped to the orange wire. If picture 1 shows a remnant of the Sony harness that was left in your MH, I would say that the installer placed a butt splice on the blue white wire and intended to hook it to the amplifier activation wire, but never finished the job. I'd take this information back to the installer and say something like: "Look at this! The blue/white wire to activate the amplifier doesn't go anywhere. What's going on with this."
You could do this yourself, but I think that the installer should finish the job and make it right. That way the onus is on him and any implied warranty for the installation is still his responsibility. I look forward to talking to you over the weekend. I'm also sending you a correction to my cell phone number. My PM has my home phone, but I intended to send my cell phone so that you can catch me wherever I am.