Do you have tinted windows? Some brands/makes are made with metalized films that mess with reception.
It sounds like you have a plug and play model if you're getting power form the cig lighter. there won't be any power/grounds to mess with.
I installed a plug and play sirius on my girlfriends car with no problems. Install was just mount the antenna (at least six inches away from a window), run the antenna wire, plug in the power, and find a static free radio station to filter through. What sirius radio do you have?
Thanks , I think it didn't want to work right because the antenna is in the rear of the Xb and it's too far away to pick up the signal from the sirius unit . What I ended up doing was running directly into the AUX jack between the seats , thats seems to work for now . I let you know after it's been on for a couple of weeks.
I don't think it should matter how far away it is, since the antenna plugs directly into the unit. That is if it's one of the units I think you have. Now if the unit picked up the antennas signal wireless then it would be a different story, but if it works nows then it's all good.