06 GMC Sierra Accessory Circuit

06 GMC Sierra is an extended cab 4x4 2500 6.0 L with sew aside doors. This truck does not have the traditional accessory circuit found on older GMC/Chevrolet models much to my dismay. Instead the wizards at GM engineered a timed accessory circuit that is wired into both front doors and eliminated the accessory position in the key switch. First I would like to know if this timed accessory circuit is controlled by a relay the computer or a module? The next question is how do I tap into this circuit to feed my XM and a control wire for my external amp to power a subwoofer. This is why I ask, when you turn the ignition switch off and do not exit the vehicle the stereo stays on and my XM turns off (because I have wired it to a keyed circuit in the fuse panel at the moment). I have not installed the amp yet because I need to overcome this problem first. I have researched the pin out on the rear of the factory installed cd/am/fm radio GM PN 15850275 Delphi PN 28043565 to fined that the 24-Way F Micro-Pack 100 Series (GN) GM PN 12110088 has a radio class 2 serial data wire OG color in Pin A1 Circuit 1044. I assume that this wire interfaces with the computer for the antitheft feature. I have tested the A3 pin (rear seat audio enable signal) no voltage or ground. I also tested the B3 pin (radio on signal) that gave me battery voltage with no on off. So this leads me back to the drawing board on where to tap into the timed accessory circuit. Anyone want to tackle this one?     Hook em up sparky

"Wow" thank you for the fast reply nouse. This truck does not have a factory amp so its off the ignition harness. U ROCK! Hook em up sparky

In the BCM under the steering column you will find a dark blue wire in cavity B3 of the 24 pin gray plug. This is a 12 volt source of RAP (Retained Accessory Power). You should use this to trigger a relay to control anything else as the BCM may not be able to handle the current demands of anything hooked directly to it. If there is no wire in the plug, you can get a wire/pin from a GM radio plug (same pin) and insert it to use. sparky

Thank you Sparky this is exactly what I needed! I surmised that a relay would do the trick just needed the pin number, color of wire and location of the BCM. You saved me a trip back to the dealership thanks again. You all ROCK! Hook em up sparky