car stereo

im looking to put an aftermarket head unit in my grand am gt 2002, but im confused as to if there is already an amp in the trunk....if so i need a special harness so that i dont run the amp power of my head unit and amp in the back.....is there a seperate amp in my grand am...help please?

That depends on the original system installed in the ride, and what year your ride is. Factory units are "packaged", some have back-end amps, some don't. What was the factory unit? What year ride?

That may help some guys who know this better help out better.