I have a 89 firebird with the 20 pin connector plug and i just got a radio out of a 95 firebird but it won't power up the radio is fine i checked it at a local junkyard so what do i have to do is the wiring different on the 89 plug compared to the 95 i means is the same plug it plugs right in just don't power up please help any chematic would help too !!!!