New owner

I have two questions: first, I am hearing a clicking noise in the passenger door(?) about every 10 seconds which I think started the first time I used my remote. My mechanic says everything looks great under the hood, but his equipment won't read the sensors on my model (2001). Also, it is equipped for a CD changer in the trunk--does it matter exactly what brand I get? Does it need to be a Bose? Thanks for any advice,
Krush

Check ot stereo shop before purchasing! Apparently, there are a couple of kinds of changers, one works, one doesn't. (This was on the '98, yours maybe different)