i recently was helping a friend install an aftermarket headunit in an 02 grand am and the new unit wont turn on. so i put the factory unit back and it didnt turn on. what has happened here? i normally install headunits on older cars and i never ran into this problem. any ideas on how to fix? i believe its the security but i dont know how to fix the problem

blow a fuse?

no no fuses are blown

is the acc wire live? did you test it to make sure you dont need a fuse tap?

You sure you have voltage on the acc, constant, and a good ground?

ok it seems as if he didnt have his ground connected to anything. i have no idea how the factory unit was running. but i ran a ground to the firewall and now its working thanks guys

Pics or it didn't happen.