My car doesn't have a trip computer, but when I popped the trim around the radio off, there's a black box to the right with a wire harness plugged into it. What is this?

it's your seatbelt timer, it makes teh chime and the "Fasten belts" light come on for a preset amount of time unless the driver's belt is buckled. You don't need it.

Thanks.

I still have mine in my car, I think I was one of the original people to actually KNOW what that thing was :-p But yes, no change if you unplug it (my chime is disabled though... so maybe it would change that) But take it out and toss it, you dont need it

It seems the clock is also wired into this harness. My clock has been acting weird lately, so I cleaned off the connections, and the clock is now working perfectly. The box looks like it will fit under my new receiver if I just shave down one of the brackets, so I'm just goin' to leave it.