Ok, I'm converted to Sirius as of today, got my old school hip hop channel back and a few others XM dropped. Here's some useful info for people that want to switch a GM factory XM car to Sirius.
If your GM car came with XM or is XM-ready and your factory radio has a "BAND" button on it in, you can switch it to Sirius. If it came with XM then you'll have the advantage of being able to re-use the factory antenna so you don't have to string one up. There are two ways to do the conversion while retaining all factory integration, meaning you don't have to buy an external Sirius tuner and have some extra box hanging off your dash or using an FM modulator so you have to go through the pain in the ass of tuning the Sirius box to one channel and your factory radio to some random FM station.
1) If your car is 2003 to what Sirius refers to as "2008 and up", you can purchase the SiriusConnect GM Tuner part SIR-GM1 directly from them. It comes with all the necesary harnesses to hook their tuner into a factory radio that is "satellite ready" meaning it has that band button. However, this tuner they sell is specific to GM cars that use the "class-2" protocol to talk to external tuner devices and in reality that's 2003 to the first half of 2006 with only two models crossing into 2007 and 2008, so do not buy this tuner if you have a 2007+ anything from GM unless it's an old body 2007 Silverado and check the Sirius compatibility list if you have a late 2006 model. Here's the compatibility chart:
2) If your car is 2007 or newer and not one of the special exceptions on the above chart, then you can't use the Sirius SIR-GM1 tuner. The 2007+ cars have switched from GM's "class-2" bus protocol to their new GM-LAN protocol and for whatever reason Sirius hasn't released a tuner for that after three years; probably some licensing issue. Fortunately there's another tuner model floating around called the SIRGM2L which I believe is an actual GM Sirius tuner part but it can't actually be purchased from them as a part, it only came in certain cars or markets. You can purchase a used one from:
GM Sirius Connect SIRGM2L
They get them from salvage cars or whatever and sell them guaranteed to be functional. I bought one with the $20 antenna adapter for my '07 Silverado, arrived two days later and seriously, it took all of five minutes to install it. If you don't intend to ever convert back to XM, you can do without the antenna adapter but you'll have to break this plastic housing off the stock connector. In my truck, the tuner is directly behind the glove box in a plastic carrier; you take two screws out of the panel under the dash to get to it, then you just push the clips towards the front of the car and the XM tuner slides right out. Push the adaptor on, slide the new tuner in, screws back in, good to go.
Since these tuners are used, you may find that you get one that still has pre-paid time left on it and you can just take it over later when it runs out; mine was already expired but signed up online and 10 minutes later I had Sirius working in the truck.
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