I have an Avic D2 with a GEX-P920XM and I just installed a CDX-P1280 multiple CD changer in my car and it doesn't function. The CDX-P1280 runs through the GEX-P920XM. The XM radio stills works but the D2 doesn't recognize the CDX-P1280. The CDX-P1280 is getting 12 volts of current up to the end of the plug that goes in the back of it but the CDX-P1280 acts like it doesn't have power. I've run the XM radio through the cable supplied for the CDX-P1280 and the XM radio functions normally so I know it's not a cable problem.

Do I need to reset the units in a specific sequence or what? Anybody have any ideas other than the CDX-P1280 is broken?

What do you mean it acts like it doesn't have power? Is there a power plug that needs to be connected, and if so is it? Does it have some LEDs that don't light up? Will it accept/eject a cd magazine? Does the headunit recognize that a cd changer is connected?

there is a small reset button on the changer near the eject button. try that

Try switching the positions of the changer and the XM tuner. So that instead of the changer running to the XM tuner and then to the head unit, wire it so that the XM tuner runs to the changer and then to the head unit. That is, if the changer allows piggy-backing of ip-bus controlled components like the XM tuner does.

the changers dont have an "in". the changer has to be the first link of the chain

Well it was worth a shot...