Volvo: aftermarket XM install, installing car stereos, volvo xc90

Question
I work for Best Buy installing car stereos. Today I installed a Skyfi Roady XM satellite radio in a 2004 Volvo XC90. At first I started to install a full FM modulator, so I took out the A/C control panel and pulled out the radio housing. I unhooked the two green plugs and the cigarette lighter plug from the back of the A/C housing. I didn't unhook anything from the back of the radio. When I found out that there wasn't a regular antenna in the car, I put all that back together and just installed a wireless FM modulator that plugged into the cigarette lighter. When I was done, the display on the dash came up saying service airbag. I heard that in these new import cars, you can't install anything aftermarket or it will do something like this. A mechanic friend told me that he just had a class on this and they said that, especially in volkswagon, if you disrupt the voltage it could fry the whole computer. My question is did I mess something up, or is this the normal reaction this car will have to an aftermarket install? Please respond to floridasprince@yahoo.com  Thankyou very much for your time.

Answer
Hey Ryan! Each module on the car is part of the computer network. Even the radio. By disconnecting one of them, you can upset the network. An aftermarket radio cannot be installed without causing problems. Some of the components will not work if the radio is removed. As long as you plugged everything back in with the igntion key in the off postion, you should be ok. If not, you may have shorted the module. They will have to make a trip to the dealer to have it checked. I hope this info helps.

Jimmy