2008 Pontiac G5, Aftermarket Stereo Install

Hello all, I recently installed a new stereo in my Pontiac G5. This is my third aftermarket deck installation ever so I know the basics fairly well but before I go making more changes I was hoping someone could support my theory of the issue. Also no OnStar or Pioneer system in this one. Essentially everything is spliced together and connected. I have a Scosche GM3000FM harness (not on their website for some reason but I have a copy of the digital manual if anyone wants to take a look) which states harness B is the one to use for my G5 2008 model. Once the car is turned on the stereo stays off without power. I tested the wires with a multi meter and found that the 12v constant yellow is good and the ground is good but the 12v ignition/accessory had no power coming to it when the ignition was turned on. I then looked a bit more closely at the harness and noticed it has 12v red coming from the chime box and spliced onto the new stereo harness but the other side which connects to the OEM harness has everything but a red 12v. Is this a common thing? Do I need to rig up a 12v ignition to the stereo to make it power on? Is there something else I'm missing?

Scosche GM3000FM- this is your problem, those and the metra axxess data harness are crap. get your self a nice pac harness C2R-GM11 for ease of use. If you go the route of a new accessory wire, you will have to use a relay to power the radio off the accessory at the ignition harness. Those cars are low voltage ignitions and could cause alot of problems if you don't33 years as a installer now just a retired old guy. Favorite thing to install/topic are remote starts/car alarms. Stop using test lights!!!

Unfortunately i have to stick with this harness. I was looking up relay diagrams on the site but ive never hooked one up before do you know the correct diagram i could use to do this? Would a fuse tap not work as well?

There is a suitable pink wire at the fusebox right side of console. It is a larger wire. Current capacity is not a problem for this wire. Use a meter to find it. Or take a picture of the wires and the fuse box and post it. If I see it I will be able to point it out.

https://directechs.blob.core.windows.net/wirephotos/acc_2442_0.jpg If you can see this picture, the red wire of your radio is only a voltage sense wire. It pulls no current, maybe in the microamp range. The brown wire may work as well. You do not need a relay. A relay draws 160 milliamps. 10 radio red wires still draw less current than a relay. Let me know if you can not see the picture I can save it and post it.

I can see the picture and it looks very similar to the large gage pink wire in my interior fuse box

Are you saying just T splice my stereo off the thick pink wire?