I don't know if you van is ride by wire or not. For my 2006 which isn't, all I had to do was add the servo unit behind the steering fluid container , and cable to the throttle body.
here is what I bought for that -
https://www.ebay.com/itm/03-07-GMC-...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
and then I had to switch the steering column switch (wiper, blinkers, lights, etc..) to one with the cruise control
Here is what I bought for that
Find many great new & used options and get the best deals for 2004-2007 GM OEM Express Savana Column Switch with Cruise Control 1999410 at the best online prices at eBay! Free shipping for many products!
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Then id didn't work, not sure why... I pulled fuses to check them out they were all fine. I went on a longer test drive and it all started to work after a few miles.
I didn't have to reprogram anything I suspect I needed a longer drive maybe for the computer to adjust to the new system or something I just don't know.
But it has been working flawlessly now.
Keep in mind my 2006 was pre-wired for the cruise - I had a plug dangling behind the steering fluid reservoir and I had the 4 pin connector in the steering column.
If you have a ride by wire van, it could be even easier, maybe all you need is the steering column switch similar to the silverado.
check this out -