Source of Switched 12V in Chevy Colorado Fuse Box

I have installed many car stereos over the years, but have run into a new problem with my 2004 Chevy Colorado. GM's new data bus is now being used to turn on its OEM radios. This means that the OEM harness no longer has a lead for a switched 12V supply.

I am upgrading to an aftermarket stereo, and I now must locate an alternate source for my switched 12V supply. [Although it is possible to hook up the switched tap on my new radio to the continuous 12V tap on my OEM harness, I prefer not to lose the auto shut-off that the switched tap provides-- eliminates risk of dead battery if myself or wife forgets to turn off the radio, etc.]

So--- here's the problem. I have checked every fuse in the box located in the engine compartment. I cannot find one circuit that appears to be switched (meaning the tap reads 0V with key off and +12V with key on/accessory). This is different than fuse boxes I have used to tap off in the past. Does anyone know if GM has changed the way they provide switched 12V, and more importantly, does anyone know of a switched 12V tap that's usable for this purpose in a Colorado?

Thanks in advance to any helpful souls out there.

Scosche sells a $100 harness adapter that will convert the new GM protocol into a standard harness pin-out for switched 12V, but that seems to me a ridiculous price just to get switched power.

Steve

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sg
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How are you getting around all of the items that are run through the factory radio? Like the door/key/lights on chimes. That data bus makes it interesting.

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Steve W.

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pika

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