The gmos-lan-04 I have didnt come with that, and the insructions for both the 03 and 04 dont mention anything like that.

 

upon reading up a little more you are correct the one I have does not retain on-star and thus it has an onboard speaker to play chimes, but it appears that those require you to keep the LF speaker on the factory amp, or mount another speaker somewhere running off the factory amp. I apologize for my confusion, I was basing it off the one i had.

 

do you have the 03 or the 04? im starting to get confused as well LOL. when i upgrade my head unit, im thinking about just getting a cheap 15 dollar Metra one and saying screw the chimes, lol

 

A few on here have done that. In fact the "key left in ignition" chime is probably the most useful, and mine isnt functional because of the amp only working on accessory power. I dont miss it.