You'll want to get a copy of the manufacturer's service manual. You can buy subscriptions to a couple of online services too, but you just rent those for a year. You don't own it, and you can't add notes. To lock up all the radio repair business for themselves, GM stopped allowing us to buy radio service manuals after the '94 model year. Those were very nice manuals and they showed the wiring and plug diagrams. You'll find the same plug diagram in the service manual. EBay is full of service manuals too at very good prices.
What you might consider first is looking for a bypass harness or connector at places like Best Buy or Crutchfield. You might also find something on eBay. There are going to be at least four pairs of wires that have to be spliced. If you do it that way, be sure to solder each splice and seal them with heat-shrink tubing. Don't use wire nuts because those don't seal out moisture, and if they work loose, you could have an intermittent connection. Many aftermarket radios can't tolerate a break in a speaker wire and will damage the output ICs. Also don't use electrical tape. It will unravel into a gooey mess on a hot day.
Another reason to pursue the bypass connector is GM often uses the same color wire for two different circuits. If you just go by the colors shown in the service manual, you could mix up two wires. At the very least that would cause two speakers to be dead. GM also uses a number of different amplifier connectors depending on the car's year and model. If you have six or eight speakers, there are usually going to be more pairs of wires that have to be added to two of the other pairs. For example, the radio will have two wires for "right front", but the amplifier may have two wires that feed the right dash speaker and two different ones that feed the right door speaker. The dash and door speaker wires have to be spliced together, then to the radio's right front pair of wires. The adapter / bypass connectors do all of that for you.
If you can't find a service manual, I might be able to find something in my Mitchell books but I'll have to dig outside in my shop, and it's 15 below right now. I'd really rather keep hibernating inside! Also, in the past I have never found the radio plugs in those books. That's why I always push the manufacturer's service manuals. I have some GM books in the house that I'm going to look at next, but I don't think I'm going to find what you need.
Monday, January 27th, 2014 AT 12:00 PM