Stan
I also purchased the correct wire adapter which comes with 1 seperate long red wire in case that my harness doesnt have the acc ignition power...
Well thas not the only wire thas not correct... lol
I hope my pics help you.
I have to pull door panels next and try to chase down
Speaker wire for the roof mounted speaker pod
And wires for the rear doors i suspect there are wires in the right door but not the left i dont have the rubber that leads from the body to the door on the left so wed. Will be another
Trip to my buddies junk yard for that rubber wire protector.
I will keep posting pics and progress.
I have to figure out all my speaker wires. Or I will be running
Alot of wire.. lol

One of the things I did already was to upgrade the speakers in that pod. If it's there, the plug for that terminates in the center of the roof line above the door. But my guess that it's not in a cargo van. My Astro was a cargo, and it had nuthin' as far as wiring goes. I find it hard to believe that accessory power isn't already at the radio.

I did try and do some of the wiring together of the GM plug, the OnStar adapter, and the Pioneer plug, when the stuff was delivered. If I can believe the GM adapter instructions, my '16 has the wires for the parking brake(for the DVD), and backup lights(for the B/U cam) AT THE RADIO!!.. That will save me time.

The factory speaker wire for the back speakers is located above the spare tire jack area. One thing you may not know is that the rear speakers, if you have both rear door and the sound bar above, are wired in parallel. The factory stereo only has 4 channels. So they bridged the back pair. That is why they use 8 ohm speakers. Once in parallel, the deck sees them as 4 ohm.
If you are doing both rear door and rear sound bar, you will need to add an amp or something, or make sure your new head unit is 2 ohm stable. Because 2 sets of aftermarket 4 ohm speaker swill be seen as 2 ohm when sired in parallel.
I uses a 5 channel amp a its 2 ohm stable. It powers all 6 speakers and my sub.

That's not a bad idea. If you're going to use both the door and pod speakers, an amp will be easier on the head unit. I disconnected the door speakers, simply because the bed and the drawers will block them, and oval speakers don't produce symmetrical sound(at 60, I'm not sure I can still hear the difference anymore, but i will still know), and the pod speakers that were 4X6, are now 4" round. I'm letting the head unit power the pod and front door speakers(separate woofer/tweeters), and an amp for the sub.

Stan.
I did notice just this morning that they are wired as parallel..... im not educated as yourself on the 2ohm 4 ohm thing... I will take your word for it...
My wiring is there in the back i removed the passide door panel... remember now I already been to the junk yard... so i scavanged the wires i need for the drivers side as well as the brackets that house the 6x9 speakers...
But that bums me to think i cant wire the pod and 6x9's together...
I gotta rethink what im going to do now...
I dont understand the 2 ohm thing for the head unit.
Tell me what would happen if i plugged the speakers in
Like they are from the factory....
No performamce
Bad performance
Blow up speakers ???

Now i havent had the time to back probe all the wires from the harness yet....
What i prolly didnt explain well enough was the harness thst says goes to my van plugs in correctly but were the yellow wire is. Acc power... isnt there... so its a universal adapter i have and its not right... i have a power wire and its in the wrong din on the plug as well... so its frustrated me
I had errans to do and will get back on it here soon.
I will post my results later.

So, there was a radio in there in the first place, right? And it worked? If this is so, then regardless of wire color, you have acc power there.

Probably the best way to explain resistance(ohms) is to use an engine analogy. If you give an engine gas when it's in neutral(no load(ohms)) the engine will rev out of control and burn up. If an amp (built in to the radio or separate- no difference) has too much load(ohms) it will struggle to make sound. If it has too little load, the speakers can blow. There are other factors and reasons that can make an amp or speakers fail, but a mismatch of ohms can contribute to loss of performance and/or failure.

Stereo Install Chevy Express Van
 

STAN.....
ok here is a shot of the connector that is factory...
YES. there was a stereo in the van ,.. and now after testing my new
unit ... The stock stereo WAS BAD... lol I thought there were blown
speakers in the doors.. come to find out the Stereo Unit its self
is JUNK.. lol
OK .. lest talk about the wires that are in the Factory connectors.
1st question.... should there be a lumination wire... one that will
brighten and dim the unit with the lights in the dash >??????
2nd we talked about no ACC wire.. thats one that activates only when the
key is in the Run or ACC position.????
I can break down all the wires that are factory for you .... that you see in this
pic... and I will once you answer my questions please.

I hope you have a multi-meter, and know how to use it.
First, I have been out of this business for quite a few years. And because of that, I don't have complete knowledge of all the different plugs. But that doesn't mean I can't help. It does mean that I'm limited by what I find on the internet, and my 60 year old eyes being able to read it. Many of the diagrams are blown up from such small images, they are unreadable. That being said, I can find little that has this plug (with matching colors) and even less that says what color wire does what. Conflicting information at best. So, a volt meter will be needed to verify the wires.

Most likely, the red with white tracer is the ignition 12 v+. The orange next to it could be the illumination wire. But then I see two other orange wires in your pic, so... I find it hard to believe that a '06 doesn't have 12 v switched, 12 v constant(battery), illumination wire, and ground. I can't believe there's a difference between cargo and passenger in an '06, especially if you found the plug in the rear( although I don't see enough wires in your pic to feed a rear harness). I had a '00 Astro cargo, and it had everything we've been discussing here(except a rear harness).

One thing should be true, and that is that the speaker wire colors should be the same color at the radio and at the speaker. And polarity of the speakers is important. Speakers have a + and a -, and if this isn't correct, one speaker will acoustically cancel out the others. So be careful when upgrading the speakers.

Sorry I couldn't be more help. If we were in the same town, I'd be there already.

Aftermarket car stereo speakers are 4 ohm impedance. Most decks have amps that put out power of so many watts at 4 ohms. However better quality ones are also stable at 2 ohms. Those that are not will overheat and fail, or have a shorter life.
When you connect 2 4 ohm speakers on the same wire, the amp will see that load as 2 ohm, and have to work harder to produce the power.
You can google a much more detailed explanation. I just dont want you to damage your new equipment.