That's a job best left for the dealer. GM has cleverly designed in a bunch of tricks to cost you money after the sale, and simply disconnecting the battery or letting it run down is a big one. If you still want to attempt it, use some type of memory saver device. There are some that plug into the cigarette lighter or power outlet, but those must remain live with the ignition switch off. Also, you can't open any door while the battery is disconnected. The memory saver can't supply enough current to run the interior lights. You should also wait at least 20 minutes after turning the engine off before disconnecting the battery. Some computers have to "time-out" before they go to "sleep mode". Until then they can draw up to 3 amps which also can not be supplied by the memory saver's little battery.
As for the cable connections, GM is always experimenting with new, unproven designs. Any chance you can post a close-up photo of what they used?
Thursday, November 22nd, 2012 AT 12:23 AM